Runs PHENOMENALLY on my iPad Air 1.
Used to have all sorts of lag and stutter throughout OS and Airdrop didn't work on iOS 9 (after clean install and restore from icloud). iOS 10 solved all those issues so rarely have stutter on keyboard, multitask, notification center, and overall OS seems faster. Btw didn't clean install iOS 10.
Just plugged in iPad at 5% and had 19hrs usage and 76hrs standby (including streaming full length movie, although lot of the other time was using iBooks/GoodReader).
Only thing not crazy about is getting rid of slide to unlock since still find that a little easier, but still worth upgrading 100%.