1) Offline functionality
Once Galaxy 2 comes out of Beta, I'd like to:
- download an offline installer (of the Galaxy2 program)
- have all game entries and their profiles (including images) available offline
2) Custom sorting!
3) Manual adding of expansions bug resolved. Or better: adding any game, regardless of it being in whatever database GOG uses.
4) Keyboard navigation
5) Disabling any social features from the game profiles (friends activity, leaderboards)
6) Editing/selecting multiple games at once
7) "sub-bookmarks"
8) Show status as offline

That's all for now. I've only had access to G2 since today, so I'm sure I'll think of more in the future.