I tried Unity and it is extremely slow and messy. Even Afterstep is better.
But it also has some interesting things. I uninstalled it, though.
Compiz can be used in XFCE and LXDE, also. But in XFCE you can mess things up
and then...a few minutes to repair it.

Here is good old Ubuntu with LXDE, Compiz and Avant Window Navigator:
sites.google.com/.../snapshots-of-linux-with-lightweigh\
t-window-managers-on-my-pc