I posted this on the Ubuntu forums, but this seemed a better place for feedback...
I ran the game both in windowed mode and full screen on Ubuntu 12.04 (64-bit). Sound worked really well, the graphics were good, even on my old Intel integrated card. No serious bugs or problems to report.
Tried out the demo mission and I like the basic concept. Once I got used to the difference between "normal" mode and "attack" mode and figured out how to equip items (I'm slow sometimes) things went fairly well. I like that if I simply walked in with guns drawn people would raise the alarm and I'd get my behind handed to me. Setting off false alarms and sneaking around got me a lot further and I like that the game encourages the player to think around things, rather than just push through.
I have a few suggestions for the next release. One would be to take a different approach to combat. Often times I'd be right beside or behind a guard and try to take aim. Either nothing would happen or my character would shoot wildly (and without apparent effect) at the guards. The few times I did manage to get into aiming mode before the enemy shot me (and broke my aim) I usually got shot before I could do any damage. My only other suggestion would be to have the player's character walk to items out of reach. Sometimes I'd right-click on an item just a few feet away and see the message indicating it was out of reach. It would be handy if items close by and in a straight line from the player's character would cause the character to walk up to the item.
Update: It would be nice if the player could shoot through windows, especially with the sniper rifle. At one point I thought I'd get smart, fought my way through a (lightly guarded) neighbouring building, got up to the forth floor and I could look across the street into the target's office. Sadly, I couldn't find any way to target people outside the room I was in. People in the office across the street and people in the parking lot below me couldn't be targeted. I guess my approach was a little too far "outside the box".
Question: After the target is shot, is there anything else to be done? I finally (after dying many times) managed to kill my target and returned to my contact in the parking lot. Nothing happens, so I'm wondering if the mission has an "end"?
Again, great concept, really nice features. I think if combat is made a bit smoother, it would be just about perfect. I'm recommending friends give it a test run.