I don't know if this bug is actually in compiz, or if it's the unity plug-in causing the problem. I noticed in powertop that compiz was using a lot of battery due to a significant number of wake-ups per second. Simply switching to classic GNOME with no effects, seems to result in a reported time left of 1 hour greater than while under Unity, from gnome-power-manager.
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: compiz 1:0.9.6+bzr20110929-0ubuntu7
ProcVersionSignature: Ubuntu 3.2.0-2.6-generic 3.2.0-rc3
Uname: Linux 3.2.0-2-generic i686
ApportVersion: 1.90-0ubuntu1
Architecture: i386
CompizPlugins: [core,bailer,detection,composite,opengl,decor,gnomecompat,regex,snap,animation,workarounds,compiztoolbox,vpswitch,place,move,mousepoll,grid,resize,imgpng,session,unitymtgrabhandles,wall,expo,fade,ezoom,scale,unityshell]
Date: Sun Dec 11 10:49:31 2011
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Alpha i386 (20110322.1)
PackageArchitecture: all
ProcEnviron:
LC_COLLATE=C
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/zsh
SourcePackage: compiz
UpgradeStatus: Upgraded to precise on 2011-11-29 (11 days ago)
Status changed to 'Confirmed' because the bug affects multiple users.