With airplane mode on, I lose between 0-2%. Haven't really checked when I left wifi on except for a couple of times, but it's usually pretty close, maybe an extra percent or two. 3G is always off, notifications/location services on for select things. This is on 5.0.1
I used to only lose a few percent overnight on 5.0.1, and tonight I went from about 65% to 30% in the morning, using 5.1. I had 14 hours of standby, and 12 hours of usage. I definitely wasn't sleep using my phone, so there's some issue there.