I experienced this right out of the gate after upgrading. I was very curious to see what my battery savings would be and decided to ditch my charger, only to have my battery gone in an hour. It's since subsided– I'm not really sure why, though at one point I did about everything I could think of short of reinstalling. I removed all kernel extensions I had added (KR4MB for example), removed SIMBL, reset PRAM, cycled the battery, etc. Now the only issue I have is about 10s after closing the lid, the fan goes nuts for another 10s before going to sleep.

Edit: Spring 2011 MacBook Pro.