Compiz doesn’t work well for every computer.  My video card for example is blacklisted since it is just an integrated ATI video card.  If you want to see if your computer will work well with Compiz, then run compiz-check and it will do various tests to see if your computer can handle it.  This is what compiz-check comes up with on my computer:

I do have compositing enabled in Metacity, but if I turn that off and run compiz-check again then it will tell me that my video card is blacklisted.  These tests give you a good idea of how well Compiz will run on your computer, if at all, before you go through the trouble of installing it.  Another nice thing about this script is that it will give you a description of your problem if you need it.  It’s definitely worth a shot if you are having trouble installing Compiz.

Via Makeuseof.com.