I have seen this question, but that question seems to be obsolete with the 11.10 version.
Last week, I upgraded from 11.04 to 11.10. I am usually using gnome desktop clasic (without effects,also called the fail-safe), because my PC is very bad. Since the upgrade, everything is so slow. I also noticed that the temperature of the graphical chip* went from 30-40 C to 60 C, so my guess that the ubuntu 11.10 demands very powerful GPU.
So, what can be done to improve the performances of ubuntu 11.10?
Logging in using fail safe option is one thing, but it is not enough.
*The temperature of the GPU can be seen from the nvidia-settings
under the thermal settings
.