New Linux Ubuntu user here.
I have a GTX 660 newly installed. I am currently working on updating the default Nouveau drivers to NVidia provided ones.
This link has been helpful:
Does the card work with the Ubuntu provided drivers? Yes and no. As for the desktop interface including internet folders etc. yeah there was an instant increase in resolution once I installed the Video Card. However, when I went to play a game, it was incredibly choppy. The default driver (Nouveau) provides lower frame rates for many of the 3D acceleration tasks games require. I'm kind of a noob I don't know, but I hope this helps.
In conclusion, if you're going to get a GTX 660 with Ubuntu, and want to play games (especially newer games), I believe you are going to want to install the proprietary nVidia driver.