I blogged a few months ago about performance improvements in nouveau, the free 3D driver for NVIDIA cards. This morning I tested with nouveau ddx from git, drm master from git and kernel 2.6.24-rc6 and used the gtkperf benchmark.
Nouveau 2007-07-13: 25.24s
Nouveau 2007-12-30: 17.88s
Quite an incredible increase in speed.
On another note, I've been able to resize my screen for the first time using the normal driver, although using experimental Randr12 mode I get this: