Yesterday I installed 12.10 in a separate partition.
I have noticed that compiz is taking a huge amount of cpu (constantly around 20%).
Compared it with 12.04 and there compiz is taking 2% ...
That's on a fresh clean install.
Any hints/tips are of course welcome but that looks like quite a serious performance degradation. The whole desktop, window management feels sluggish on my hardware (Dell Studio 1537) with 12.10.
I think I'm gonna stick with 12.04 for the time being.