Compiz is a compositing window manager that is now the default in Ubuntu's Unity desktop environment.
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Cube desktop is appealing to some users, in addition to many of the other visual effects Compiz can manage.
Compiz has plug-ins that can be enabled / disabled in order to alter its behavior.
Pro Has great wobbly windows
Pro Uses hardware acceleration - which is a solid PRO - especially in some specific cases
Con Not really useful as standalone WM
No panel, no menu - just no way to start applications.
Con Requires 3D acceleration
If this is not present in the system, it will offload from the GPU to the CPU.
Con Poor KDE 5 support
There is poor plasma 5 support in the 0.8.x versions. The 0.9.x seems a bit better.
Con Crashes frequently
Breaks in the system are frequent.
Con Heavy window manager
Compiz is one of the heavier window managers around: it uses higher amounts of RAM and CPU than other options