After years of suffering greatly, the open Nouveau driver is now as good on my machine as the old Nvidia blob driver. The main reason that nv earned the legendary finger from the Big Guy, is that they are real bitchy about opening their specs and such. They have had this horrible binary for years, which kills you every time you put in a new kernel. Now with the latest Debian Sid, and 3.6.6, I can finally play my Foobillard smoothly. (Geforce GT 520).
Of course, they claim to have upped their game with another binary. Look for years for an open driver to catch up with their latest products.