I just scanned through the bugtracker and selected the bugs I found most crucial / release blocking. Some of those make the game look like a cheap, half-broken indie game, others are simply are nightmare for players:

Can't see required construction site materials if construction site is directly over the bottom

Suggested fix by Sven2: Expand viewport clipping to outer scroll border instead of landscape border for messages.

Buildmenu texts are rendered before anything else

Suggested fix by Sven2: show non-GUI object messages behind GUI.

Pink blocks in landscape

In relation with solid masks. This is really ugly.

Energy bar disappears on GUI reset

I'd appreciate anyone have a look into the GUI code in the engine if this is my fault or the engine's. I'm out of ideas. This will happen whenever OnSynchronized() is called in objects, so I guess when resuming a savegame or after a runtime join.

Engine didn't save own controls if you restart the game

I haven't tried if this is still the case but noticed it as well some time back. This is unaccaptable for a serious game. :/

Selecting AA in options turns GUI text from black into white

Also something I noticed. Again, very ugly. If changing AA can't be done otherwise, maybe the game should require a restart to make this change.

Objects at the bottom of the map are being deleted

From a player's perspective, this is probably the worst.