It is amazing, if only because of the extent of the customizations. my favorite is f6, which will make all the windows slide to the edge of the screen so you can find stuff on your desktop. When you need the windows back, F6 will slide them back into place with a nice flourish.
Furthermore, compiz supports the feature like in osx where you can see all open windows tiled, pick one, and go to it, but it takes it further - you cna also do a ultra fancy version of the xp alt-tab, and for the die hards compiz will throw all of your workspaces onto the faces of a cube, rotate it and pop off the windows until you find the one you want.
The special window effects are amazing as well, from zooms, fades, transparency by mouseovers so you can see what's behind the current window, and even a feature where you can torch the whole window when you close it - the window actually goes up in smoke.
That's just the beginning, there's also strechable bouncy windows you can have, rain, snow, and so much more. i am quite happy to have wasted my afternoon just messing with it. it is amazing.
I got the cubespace effects working, and it is the most spectacular looking effect I've ever seen. You can, with a few keystrokes, float the current window off of the desktop in 3d, and then have it float around a cube of workspaces and drop it on another one, or even just spin around the workspaces looking for windows. Furthermore, for the times when you need a big picture, it can unfold the cube and let you look at all the workspaces side by side. i'm psyched.
the f6'd desktop. isn't it amazing?
With windows. it makes me so happy. (i need to try and figure out how to record some of the efx... but that would require video, as they really need to be seen in action.