Whoops 21:07, 12 May 2009 (EDT): I had the following leftovers when I merged Compiz_Fusion to Compiz - don't really know if it's still an issue and maybe belongs here (never encountered those Problems since the new versions of Xorg & Compiz):
Make sure that the environmental variable $XLIB_SKIP_ARGB_VISUALS is not set
Using "Texture from Pixmap" rendering
Preparing Xorg for Compiz Compiz, at this moment, has only one rendering path. The "Texture from Pixmap" path runs faster but doesn't work on all hardware yet. The GLX_EXT_texture_from_pixmap extension is needed for this rendering path. This extension is currently provided by Xorg if you either use the 9xxx nvidia drivers or the AIGLX extension. It is also provided by Xgl. Refer to the Composite wiki for more information.
Whoops 21:07, 12 May 2009 (EDT):... so if part of this is still useful information, someone might want to paste it into this article.