Comment 205 for bug 862430

12.04 being an LTS is the reason why this bug will not be fixed. If you read the older posts the developers say that fixing the bug would require a major change in compiz's core which would compromise it's stability. But compiz is an eyecandy, if it doesn't look good it's nothing. IMHO the problem is the not caring. 12.04 is a really old version and Cannonical cares only about the next version and since this is not a security issue don't expect that it will ever be fixed.
BTW also don't expect many compiz improvements in the future because with the replacement of xorg compiz will become outdated. It's a shame though, compiz indeed used to be the best looking, most configurable window manager and it had the best multihead support (which is unfortunately also considered outdated).