I was having the memory leak problem that caused the home screen to not refresh correctly some times....so far I haven't noticed that. I'm still keeping an eye on battery life. It got worse on 5.1, but I also added two new bluetooth devices at the exact same time (and previously almost always had bluetooth off), so I couldn't tell how much was due to bluetooth vs. 5.1. So far, batter appears to be a touch better even with bluetooth on.
I did not do a factory reset after either installation.
~Gary