These basicaly enable you to use the 3D power of your graphics card, on your Linux desktop. Some of the effects are pure eye candy, while others are pretty damn useful.
For an easy way to test how well they work on your laptop, you can download this Live cd that needs no installation. It’s a Kororaa distribution, that’s based on Gentoo with XGL & Compiz already installed & running. You’ll just need to burn the image to a blank cd & leave it in your drive. The cd will autoboot the next time you turn your computer on.
Please bear in mind, it won’t be running full speed from the cd & that these are older versions of XGL & compiz. The newer versions should be even better 😀