The various GUI windows take up a lot of space, without providing that much information.

The battle management unit view doesn't expose all the stats like the movement points of the units, the portraits take up a significant amount of space within it; 

the top right empire thingy doesn't feel needed in battles if they're supposed to take a long time, overall with the top battle information this adds up and reduce the area where the player is getting actual terrain info from to around 50% of the screen

Attack prediction is pretty big, but its position at the top doesn't feel as noticeable as e.g. at the bottom

While flattening the terrain is good, throught the whole first scenario I thought the forests were stones because of their appearance; perhaps instead of just flattening tiles could also be changed to more primitive icons

The contrast between deployment zones, and fog of war/normal terrain didn't feel sufficient as I caught myself trying to position units in the enemy empire's deployment zones, and fog of war on nearby tiles often went unnoticed.

The unit animations at times didn't feel quite right at times, when horsemen attacked my trebuchet, at first I wasn't sure if it actually got hit or if it was a movement glitch and they moved to the tile next to it

A few times I found myself trying to order a unit whic refused to do something because a different unit was still in the end stages of its animation, some kind of queue system would be handy

And as the last point, the sound felt like it lacked something. The music was a bit too peaceful, the unit sounds were quiet and sparse etc. this left me feeling a bit bored during the combat even though the combat itself was fairly captivating when it was my turn

This: The contrast between deployment zones, and fog of war didn't/normal terrain didn't feel seufficient as I caught myself trying to position units in the enemy empire's deployment zones and fog of war on nearby tiles often went unnoticed.