iPad iOS 9 Performance
I've also been using the iOS 9 update on three iPads: The iPad Air 2, iPad Air and iPad mini 2. So far, so good.
I haven't run into any major issues (Touch ID is working fine on the iPad Air 2), all three of them are fast (even the iPad mini 2), battery life is outstanding, I haven't noticed any issues with Wi-Fi or Bluetooth, and I haven't experienced any catastrophic experience-breaking bugs.
I've said it before and I'll say it again. iOS 9.1 is the most stable version of iOS 9 and that applies to all three of these iPads. If you're already on iOS 9, I think right now would be a great time to make your move. After some prep work of course.
If you're on something older, the decision is a little more difficult but I think iOS 9's iPad features make it a worthy upgrade.