The iPad Air 2 is not worth the upgrade if you already have the Air 1. Aside from the enhanced hardware, better camera and Touch ID, there simply isn't anything compelling. The Absence of NFC relegates Apple Pay to being able to make App Store purchases, without having to type in your password.
Anti-reflection screen coating; Faster processing; More RAM; Wireless Connection is faster; Touch ID
Very Minor Upgrade; No Mute button or rotation lock; Apple SIM does not work in Canada or Australia