I did it right away because my back up from my 6 was on 9.1 and I wanted to restore from it. Anyways I did use it a bit between the tmobile store and the restoring process and found some of the lag and freezing that I am now seeing people complain about. After going 9.1 b2 it is so fast and buttery smooth I keep telling my wife how this is the first yearly S upgrade that I have bought that to me felt like it was justified to upgrade. Anyways do it and enjoy.