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.
The primary cause of high GPU usage in an idle Ubuntu 11.10 desktop will be compiz, the compositing window manager. You may be using a compositing window manager even if you are using the GNOME Classic or Unity 2D session instead of the default Unity session To check if you are running compiz, you can run this command from a terminal:
To switch from compiz to metacity, you can run:
Since this happened after upgrade from 11.04 to 11.10, another possible cause for GPU regressions may be the video drivers themselves. You may want to check in the "Additional Drivers" tool (available from the commandline by running "jockey-gtk") that you are running the optimal driver for your card. There may be several different drivers available that support your particular card, and you may find that one or the other provides better GPU performance. For some older cards, it is even possible that the 3D acceleration provided by the open source nouveau driver may be your best bet.
Posted as per request of the OP.
As for CPU usage, Ubuntu 11.04 shipped with kernel 2.6 while Ubuntu 11.10 comes with kernel 3.0. Your problems with CPU may possibly be due to that. Try googling your processor name for any bugs with Ubuntu 11.10. It's probably not your case but, as an example, Sandy Bridge processors have some power issues with most recent kernels.
If you still have kernel 2.6 installed (it should then still be on the GRUB menu), you may try booting into that to see if its any better.
Remark: I've actually misread the question initially thinking that you have a problem with the processor (CPU) heating itself. I'm glad that it worked anyway. However, since previous kernel does not have any issues with your GPU, the problem may well be due to different drivers as @slangasek suggested and you should refer to his answer for this part should you want to try fixing it.