Running an Inspiron 700m so I have an 855GME and have applied your guide and upgraded to the latest kernel/driver/etc. I do see the performance increase in ppracer. [Note I had not tried just turning on UXA under the default setup, but that is 2d and doesn't related to 3d]
My issue seems to be related to closing a graphics app. If I close ppracer (3d) it hangs. If I close world of goo (2d I think?) it hangs. If I play a flash video and close that tab it hangs. Note first I thought it was X hanging in the case of the games, but if I launch the game from a terminal, then I can kill/close the terminal to close the app (note I can't terminate the app directly)
Video does seem to play slowly in Totem... but fine in VLC and Flash (although Flash seems to intermitedly stick and needs a boot, by moving the slider on the movie timeline, to unstick it).
Anyway... at least for the hanging games, at least I have a way to play them without having to reboot and more importantly a way to reproduce this problem without needing to reboot as I look for a solution.
If you have any suggestions for running a debugger to identify what is actually getting stuck (driver/x/whatever) I'll see what I can do
[OK I've had a couple hangs launching ppracer... weird how it worked well for a while and now just doesn't with no change that I know if]