5.1 so far ok-ish for me.
- Battery life is marginally better, but it looks like more than any real changes, they just tweaked the indicator - before the phone was really fast to drop from 100, and last 5% would last for hours. This time the initial drop from 100% takes forever, but the numbers go down quicker below 20%. The final result is the same for me with slight improvement - phone lasts about 2 days when in the same house/area, with moderate use and no gaming.
- Battery wise - the infamous "snitch connection" to push.apple servers still doesn't jump from 2G/3G connection to Wifi, when Wifi is established, which means 3G radio never properly sleeps. It also reverts back for polling to 3G when phone sleeps, you can see it for a second when you wake up your phone, it shows 3G icon, then re-enables wifi. It should be the other way round - turn off 3G and let wifi wake up when phone polls in sleep mode. Wifi eats less battery. And I can't think of a single scenario where switching on wifi shouldn't = automatic switch off mobile data over 2G/3G. This phone could go on for 5-7 days in 2G mode without charging if it wasn't for this stupid thing.
- GPS drops out more often than before. Takes longer to pick up signal after tunnels as well. Let's blame it on sun spots for the time being.
- Jury is out on this one (could be in need of reset), but mast jumping seems to be not working properly. Since upgrade when I move around (cycle, drive) my phone tends to drop connections during active calls approx once every two hours, bars disappear and I get "searching" in task bar just for it to return to 5 bars few seconds later.
- Looks like pin lock is useless now, one can open camera from home screen, and then move to browse gallery/camera roll with all the options without unlocking?