Played the game a LOT over the last few days.  I played as the UE for the first 2 games on hard and serious and the next 2 games with sophons on impossible.  Won the first 2 games rather easily, was effectively dead by turn 40 in the last 2 games.  

Edit: played a 3rd game with Sophons on impossible and spawned next to the UE and the Vodyani.  They were both kind enough to go to war with each other and leave me alone.  I won this last game.  

I'll break this down by sections for readers sanity sake:

Racial mechanics:

I LOVE the idea of all the races being asymmetrical in their gameplay.  I have only played the above 2 races, so this will be more of thoughts of and comparisons between the two.  The UE is a solid faction with a very good game plan.  They specialize in industry and expansion, which makes for a solid early, mid, and late game.  I ignored the economy techs and used 3D printing to make up this difference.  The first game I started steam-rolling very early and abondoned the game to start up a new one on a harder difficulty.  In serious difficulty, I was steam-rolling the map by turn 75ish.  The faction ability to turn industry into influence and to use influence to buy things is very strong.  Industry in general is a cornerstone of any 4x.  I really liked the UE playthroughs!

I was playing on impossible with the Sophons, but they seemed very weak in comparison.  Their specialty is science, but even if they have more options of things to build sooner, they still have to build the improvements or upgrades.  They do not get any bonus to industry to help them do this.  In the early game, it just feels like they have more improvements they could build, but probably shouldn't unless they are being ignored by all their neighbors.  Their starter ships are also terrible, meaning they have to sink more production into ships early to make up the difference during the initial map control and system grab phase.  In multiplayer, I suspect they will be weak, but I am clearly not an expert and may be approaching them incorrectly.

Edit: read about wonders on a forum post.  The Sophon's being able to research wonders first might give them a good advantage come mid-game.  Depends on what they do I guess.  Are they still confirmed for the release version?

Being able to quickly research an era 2 tech doesn't help, because they are all too costly production wise to build in the early game.  Also, why does the smartest race have such inefficient ships?  These guys are supposed to be scientists who love finding new ways to blow things up and new ways to improve system efficiency right?  If we were talking about a fight with melee weapons, them being so weak in combat would make more sense.  But the Cravers, who lore-wise are much dumber on the average are able to make better ships than the Sophons?  In short, their science aptitude does nothing for them early game and their ships further hamper them.  Perhaps they can turn the science bonuses into  a snowball effect late game, but I feel like their basic industry and slower start will bottleneck their superior tech.

Perhaps they need a trait which gives them bonus industry with their science production or some such boost.  They could be finding ways to optimize the drudgery work with science to accomplish it quicker and easier?

Edit: played another game with Sophons last night, was fortunate enough to be right left alone for a while and started to steamrolled the map around turn 100.  They still feel weaker than UE.  I had like 8000 influence I would probably never use.  

Combat:

I like it overall.  With tier one weapons, OPAL lasers feel OP compared to the rest.. Also, the weapons which only fire in close range only (beams I think?) seem pointless.  Does a ship's movespeed affect how fast it moves in battle? Perhaps a lot of engines could be used to quickly close distance to a range where the short range weapons will have an advantage, but this is the only way I can see these working well in the current system. The weapons are good for what they are, although they are a little vanilla.

Perhaps adding in more mechanics might make the ship design and battle results more interesting?  As an example: let missile weapons attack no matter what direction their mount is facing, increase their damage, and let the short range weapons act also as point defense vs missiles.

The big issue is that you want your ships shooting broadsides as quickly as possible.  The time it takes for ships to close to mid or short range is time a lot of the ships guns are not firing.

The graphics and sound effects in combat are really well done.  I like how every empire has different ship designs, aside from how gimped the Sophon's starter ships are haha.  Maybe they need to be and I'm just playing them wrong...  But I wonder if their ships are weak because they are science nerds and that's the stereotype.  Which again, would make sense in a fist fight, but not in a "who can build better ships" fight.  

I liked the pirates, and feel they are at a good strength level from what I've seen.

Edit: they start good, but perhaps need to scale better as tech improves?\

UI and artwork:. 

Rally, this is just a short praise section.  Amplitude has done amazing things with the UI and their unique artwork since ES1.  The quality of work you guys put in is evident in ES2 as well.

Tech:

I love the idea of empires compromising their techs for their own race and abilities, but a LOT of the techs feel like must haves for any race.  I'm not going to say much here given that the tech tree is already being reworked.

Faction quests:

Some of the options for main faction quests are just MUCH easier that others, which I feel will lead most play-throughs to feeling more the same.  UE's first choice between manpower and the other options for example.  Aside from that, really like the inclusion of these quests in the game.  The search for the academy of the endless seems pretty difficult given how rare atmospheric disturbances are.  But, that might be a good thing as everyone gets the same quest at the same time?

I really like the idea of Sophons having science labs on their ships as a bonus module!  This should also give a political science bonus per ship built, and the added utility will make their ships less terrible in general.  Science bonus and political science bonus should scale with hull size.  In other words, ships should boost both science and military ideology.  Explains why their ships are weaker (they put more hull space and thought into having good science labs on their ships), and contributes to their science by producing ships.  The ability to build more ships and still keep their science political party alive would be really nice, given that if the opponents are smart, the Sophons will need a fleet anyways so other players don't just conquer them for free so to speak.  So, the necessity of building a fleet for defense if nothing else will not push them as strongly towards military policy.

The new tech tree might make their ability to jump to the next tier more useful with the new tech tree, as it is now, like previously mentioned, there are too many tier one techs needed, and the tier 2 techs cost both too much science to research and too much production to use in the early game.  In the early game, you just don't have the production due to no upgrades and a small population to produce tier 2 system upgrades in a timely manner.  Sophons cannot afford to spend 20 turns making a tier 2 system upgrade in the early game for 2 reasons:

1)  4x games are based on geometric growth, so losing map control and thus being behind on the expansion phase of the early game will have large consequences later if the opponents are playing smart.

2)  Most of the tier 2 techs are population based anyways, i. e. +2 X per pop.  In the early game, you don't have the population to really take advantage of most tier 2 tech anyways.  Maybe Sophons should get access to the basic ship weapons and defensive tech from an era ahead as well as being able to research techs from an era ahead?

While Sophons have bonuses to science, just expanding will give any race bonuses to science as well as the other FIDS.  Unless a race has the ability to do more with less production and/or systems, they need to stay even with the other opponents in terms of expansion and colonization just to stay competitive in the game.  So, do the Sophons get more bang for their production buck from their science bonus?  In other words, how much does their science bonus help them?  I feel like they are missing something in their game-plan and racial mechanics, but I do not have much experience with them in the late game.

Edit: also...

In multiplayer, (and assuming players are all starting rather close to each other, i.e. many races on the map and the map isn't huge, which you probably wouldn't want a giant map on multiplayer anyways), I suspect that everyone will want to have some form of military early in the game.  If you don't have any map presence, you can't contest anyone over a system.  They can just blockade your colony and ensure they get the system.  Also, they might just decide to come take over your empire if you have no defense and they built ships early.  The Sophon being able to boost their science production and politics by making ships would help them out and be a unique mechanic for them.

But the delay to construct a colony ship are way lower than the 5 turns you had to wait with ES1 ?

Turn 1 of a new game:

- Player A & B have 1 planet and try to settle to the next one (admitting they found a colonisable planet just next to where they are).

- Player B's ship is zapped for a reason or another (risks are low but let's say this is it).

- Player A have to wait 10 turns to settle.

- Player B is now only say 3-4-5 turns late on this, because he've got to reconstruct his ship then re-travel and settle.

BUT the first 3-4-5 turns of the game provides with a 3 man planet + 3-4-5 turns with a 1-man planet provides, say +/-150 FIDSI ?

AKA Player A is a couple of events / a couple of probe / whatever ahead of player B ?

That's why you're talking about production, not growth.

Player A won't growth 10% or X% faster than player B for the whole game: on this exemple, player B is just late on production for a couple of turns, travel time and the price of a colony ship x 2 (the one that Player A could produce by that time + the one that player B had to pay).

Growth is acceleration, production is speed, the two things are related, yes, but these are not the same.

In your example, having to make another colony ship in the very early game is more like 7-8 turns of production.  Early game, you have the drone and cyber reality upgrades to make and perhaps a ship or 2 to pump out for map control/exploration/colony protection.  Adding 7-8 extra turns either slows or alters the players plans/options.  What if another empire settles the same system and your military can't break their blockade due to the wasted turns of production for example?  And I am not saying that the growth is hugely exponential in practice, only that increasing your production increases the amount you can spend on expansion, which increases production faster, which is cyclic.  It isn't game ending by any stretch to lose a colony ship or colony early, but it does hurt more than just a few turns penalty when compared to another player who didn't have that setback.  Anyways, this is a minor point.  I will agree we both have valid points, and are probably seeing this from different points of view/play styles.  I am very expansionist and industrial when I play 4x.  

I am more worried about combat and race balance currently anyways.  As I said above, Sophons feel pretty weak, and combat currently needs rework.  I was playing Lumeris, and my scout with the starter mass driverish weapon went against an EU scout with the same weapon.  Ideally, we should be fighting at short range, but I picked sniper, which didn't fit my weapons and dominated the opponent who selected a short range strategy which did fit his.  Both of our ship's guns were on their broadsides, but mine was able to get extra damage in at first from long range while the enemy ship was trying to close to short range and didn't have my ship in his broadside field of fire, then the opponent got close enough to shoot and we were both in our optimal weapons range.  By then, it was very one sided.  

The inability of ships to use most of their weapons (their broadsides) at first while they are trying to close range is a pretty big disadvantage.  The shorter range weapons should have more DPS to make up for this, but seem not to except for the beam weapons which ONLY work in short range.  Seems like selecting long range engagements to instantly be using broadside attacks with long range weapons is the best way to go by far.  It is possible with larger fleets, you can soak the long range fire long enough to get a good advantage.  My game won't make it much past turn 100, so I don't have a lot of large fleet battle experience.  I hope this gets balanced or addressed in the combat update if it is as big of an issue as I see it to be.