Hmmm, just tried RC 7. Seemed fine until I noticed I could hear my system fans. I tried going back to RC 6 and RC 2 but they all want to idle at 6% to 27% CPU. When actually doing something CPU usage easily hits 60%. Seems like some wheels are spinning somewhere. I'm not unraring any files or doing a repair.. just getting headers. Even so, when it settles back down to idle the CPU drops down to 1 or 2 percent, but only for a few seconds. That it bumps right back up to 6% to 27% range just idling.
edit: strange.. but when actually downloading a large file it doesn't seem to exceed 11%. Sitting at idle it jumps to 27% or so. Kind of unexpected behavior. Anyway, it's downloading headers fast so if it goes a little crazy for 2 or 3 minutes it's no big deal.