One thing to note about Compiz development is that it no longer happens in GIT. All of it is happening in BZR from now on.
I would hardly say that compiz is dead though. I'm running Compiz-0.9.7 in Archlinux right now.
Compiz is fast and stable over here ~ but i am using Nvidia + only the plugins that i need.
I've also been experimenting with Cinnamon/muffin ~ but much like GS - i experience xruns / glitchyness when using either actitives (in GS) or the 'scale' plugin (in Cinnamon). Compiz still works the best for me in this area (although, it used to cause issues way back when).
It'll be interesting to see what the cinnamon devs do over time... for me Compiz' selling points are the vast array of 'useful' plugins, that pretty much have no counterparts are found in GS/mutter/Cinnamon/muffin. Although, KDE/kwin has similar features - it's way too much bloat and i don't want to pull in kwin on a non-kde desktop -> although i could be wrong, and someone can correct me if i am wrong -> it probably has some hard dependencies of KDE related packages.