Intel has released a fascinating new utility that reveals what is preventing the CPU from going to sleep/low power state. A few of the bad actors I found on my system so far are ipw2200, hald, and audacious. hald appears to poll the disk constantly for something so it’s ide0 that appears active but not hald directly. Audacious causes 160 wakeups-from-idle all by it’s lonesome. Finally, when everything else is inactive my wireless driver (ipw2200) keeps the CPU awake constantly. If I’m plugged into a hardwire connection the CPU can sit in C3/C4 for greater than 90% of the time.