FIX: low FPS feel despite high performance. Please Read.
To anyone using the beta, have you felt like the game is running low fps, even though your achieving decent frame rates?. Example: 60fps feels like 30.Almost like microstutter for those who have used SLi/Crossfire.
I found the issue related to how Compiz and the nvidia drivers detect refresh rate. There was a bug report for this posted. For me the issue was resolved by making sure Vsync to blank is disabled in Nvidia XServer and then installing the CCSM manager and manually setting the refresh rate. You can find it in the Software Centre, or alternatively install via the terminal.
Once in CCSM manager, navigate to composite.
Check "Undirect Fullscreen Windows"
Uncheck Detect Refresh Rate.
Manually set the refresh rate to 120. (Im using a 60 hz monitor (Dell U2410), but setting it at 60 still produces the low fps feel.
This completely solves the issue of the game feeling choppy or on low fps and makes the game as smooth as it runs on windows. I'm not an expert, but im sure this is related to the latest compiz and Unity on ubuntu.
I feel its worth throwing this issue out there as some people might not even realise its happening, but for me, the game was unbareable without this fix.
For the Record, the machine specs are a 680 GTX and i5 2500k @ 4.6 on Ubuntu 12.04 using the latest 310 experimental driver from nvidia.