With the less demanding OpenArena game, at 800 x 600 the Nouveau driver performance more than doubles for the 8500GT, 9500GT, and GT 220 with KMS page-flipping. In fact, for the GeForce GT 220 it is a 3.46x improvement over the page-flip-lacking 2.6.38 kernel.
When the OpenArena resolution is increased to 1920 x 1080, the Nouveau driver is faster than the NVIDIA blob on the GeForce 8500GT. With the GeForce 9500GT and GT 220 the performance is nearly as fast. For the 9800GT, there is nearly a 300 FPS difference. Besides the Nouveau driver gaining much ground against the official NVIDIA Linux driver, the 2.6.38 to 2.6.39 boost is enough that at 1920 x 1080 these ioquake3 games go from being barely playable (30 ~ 40 FPS) to being able to easily handle the OpenGL load fine (80~100+ FPS).