Hey Numerlor,

As you guess, you may want to sync your account on more time've if you just buy a game or unlocked a Steam achievements. We're working to improve the experience, to automacially detect when you've unlocked something (games, achievements, ...). But the SteamAPI doesn't allow us to attach hooks or triggers, so we're still working on something clean to do this. We're also concerned about privacy, and we try to avoid as much as possible to "scan" you Steam data without your explicit consent.

So short answer: you should manually sync your Steam account to activate some new stuff :)

DarkHerumor