Victory
I got beryl (i.e. compiz-quinnstorm) working. I had to do this:
export LD_LIBRARY_PATH=/usr/lib/opengl/xorg-x11/lib
export DISPLAY=:1
beryl-manage
This thread was a life-saver. Now rather than the whole screen being white, I get nice unnecessarily bouncy window effects. Can't be beat. A lot of new stuff has been added since last I looked. The development speed on this project is rather shocking. Every time I look there's a new plugin or new feature that's been ganked from OS X or Vista. It's an exciting time to be a Linux user.

sudo apt-get remove compiz (and its various other packages) and then sudo apt-get install beryl (and its various other packages) did it for me. :)
Too bad it requires you to forfeit your soul.
“emerge beryl-core” did it for me. Other than the whole library mismatch thing.
Don't you want to rejoin us Ubuntu heathen?
I was actually considering it. Then I read that ubuntu's x86_64 support sucks. And I realized Gentoo works fine and runs everything I need it to, so there's no point in switching.
If my Gentoo install ever has a catostrophic failure, I may consider switching. But if it hasn't broken given the amount of abuse I currently throw at it, chance are it's not going to any time soon.