I just remembered I had an odd problem this morning:
Fully charged my phone last night, and set an alarm for this morning. My alarm never went off. I later woke up and looked at my phone. Pressed the power button and the lockscreen wouldn't come on. So I pressed and held it and the phone booted up. I thought that I had perhaps accidentally turned off my phone last night, but then I looked at the battery meter and it was at 13%. So apparently my phone somehow shut itself off last night? I looked at the wakelocks and screen usage and they were minimal, like 1 minute for the screen on time. This is a one-time problem though, but just a heads up in case someone else gets it. I'm on 2.2, since I still can't flash 2.2.1 (bad file error) but I'm working on it.