Finally, thanks to the CSMT patches (aka "performance enhanced graphics) this title actually works and it's fairly playable. Average fps on my rig is 50-60 (peaks to 80-100) fps but... there are drops to 25 and 30 when looking around which translate to stutter. Play with vsync off. Water has a tendency to disappear.
My computer has an i5-2500k CPU, 8 GB of RAM and an Asus GTX 660 with a tad of factory OC and the DirectCU II custom cooler. Testing is done on Ubuntu 12.04 64bit.
If you disable CSMT the game will run for a little while and then crash.