I’ve written a couple of times before about desktop effects and the how to set them up. I won’t cover that again but will add a couple of things I have learned since then.
There are options
First is Compiz Options. These are found by right clicking on the Fusion Icon in the Panel. There are two options and one I use is Loose Binding. Not sure how it works but it does make a difference to performance, at least with my nVidia card. When it wasn’t selected performance was slow and X was working flat out, taking up around 30% of the cpu. With Compiz using about 15 – 20% that was quite a load. Now compiz is about 25 – 30% and X rarely over 1%.
There were other benefits too. I often found the screen totally messed up when resuming from Suspend. The only fix was to reload Window Manager, again using the Fusion Icon. Now that problem has disappeared.
I guess the lesson here is test the options, the other one is indirect rendering, and see if they improve Compiz on your computer.
Pager
The second thing is the pager. I use KDE 3.5 on Fedora 8. That is the bar that shows the number of desktops you have and allows you to click on one to bring it to the front. The standard pager refused to show the four desktops, it was stuck on one. I removed it and installed the KDE one designed for compiz, kicker-compiz. After adding it to the panel I had four desktops showing again.
As an aside there is a great option in Compiz called Window Preview. You will find it in ccsm under Extras. It shows the contents of a window in the Pager as well as when you hover over the application name on the Taskbar.
Techodyssey 
“Loose Binding” updates the checking on the display for its consistency with what’s happening much less frequently; once every 6-10 frames instead of once every couple of milliseconds.
that explains the performance improvement. Thanks for the info.