I have all kinds of problems with Bluetooth, specifically with pairing or connecting devices. Hibernation is all kinds of wonky, too. If it's been asleep for a few hours, it will hibernate when I plug it into AC power without resuming it first. (I really wish there was a way to tell it to hibernate if it's been suspended for some user-settable amount of time like I can with Windows, but that's not a problem specific to Mac OS X 10.10.)