1.
Game Version: 1.2(I think? Whatever Steam's latest update is)
OS: Linux: Elementary OS(Ubuntu 14.04 fork)
CPU: i7-2600
Ram: 8gb
Graphics: NVIDIA GeForce GT530

2.
Graphics work fine

3.
Amagi82

4.
I belive you have a rather serious memory leak. When I first load the game, it uses about 800mb of RAM, and after an hour or two, that amount slowly creeps up over 2.5gb, and the game slows to a crawl, and eventually becomes unplayable until you shut it down and restart. Happens every time I've played so far. After observing the system monitor, the most noticable jumps occur during loading between heists.