Phoronix tests the performance of the open-source Noveau driver with the $10 XFX GeForce 9600 GSO graphics card, you can check it out over here.
"In this article is a look at the state of the open-source
Nouveau Gallium3D driver on low-end NVIDIA GeForce graphics hardware. In
particular, a $10 USD NVIDIA retail graphics card is being tested under
Ubuntu Linux on both Nouveau and the proprietary NVIDIA driver and is
then compared to a wide range of other low and mid-range offerings from
NVIDIA's GeForce and AMD's Radeon graphics card line-up with a plethora
of OpenGL benchmarks."