Probably all been said by now but the ones that I keep noticing are these: (iPhone 6 Plus)
1. Can turn on Bluetooth from control centre, but can't turn it off. The button does go dark but Bluetooth stays on, have to look inside settings.
2. When I open the app switcher, it starts normally but then almost immediately shifts everything to the left so that there is a lot of space to the right of the current app. Kinda annoying because I see it and go to press the one behind it and then it moves so I end up selecting the same one I just tried to switch from.
3. Can't seem to open a notification from the lock screen. Swiping doesn't seem to do anything but swipe to either camera or widget screen.
Apart from those, there's just the generally twitchy nature of the whole thing but that's to be expected. Battery drain scared the crap out of me at first but turns out it was because it was downloading a bunch of apps so no worries.
Oh and when I use the one-handed keyboard (great stuff), it changes back to the normal full-width keyboard every time I sent a message which sucks.