FYI a bug which apparently surfaced during beta but Apple didn't fix was a computer that wouldn't go to sleep. Shows up on my nMP, but not on my other macs, and showed up on other computers by report. The problem is that the computer will wake itself up. Looking in the logs shows a "RTC" wakeup (Real Time Clock), basically an alarm. I got Apple on the hook in the bug reporter and after some research traced it down to this http://ispire.me/fix-yosemite-rtc-alarm-wakeup-issue/ I'm not sure how this individual found the workaround, but disabling multicast discovery (bonjour among others) will temporarily fix the issue. Of course then you also lose auto discovery. FYI - it's a logged bug with enough clarity that Apple should be fixing it. For a temporary work around see above.