I think it's the other way around--it's a shame Gnome chose to built yet-another-window-manager instead of building upon the solid and tested Compiz. Very NIH-y of them.
(Though Compiz most certainly has been on a measurable decline since the Natty days. The same laptop ran Natty without a hiccup, but it runs Gnome Classic on Precise with at least one Compiz crash every few hours. Not to mention the many bugs introduced into plugins since Natty--window previews and wobbly windows, I'm looking at you.)
