I have several iPads at home. Brand new Air 2, and old Air 1, mini 1, iPad 3, iPad 2.
The Air 2 is awesome in terms of thinness, but does not feel much lighter than my Air 1. The 2 GB of RAM is extremely noticeable. it is great not having to reload webpages any more. Even after a day, and doing a bunch of other activities, surfing other sites, etc., the original tabs with lots of pictures, etc. still remained in cache without ever needed to reload. Forms stay filled out also.
Speed wise, Air 2 is faster than Air 1, but Air 1 is still a decent machine. iPad 3, 2 and mini are virtually unusable with some apps on iOS 8. I will be selling or giving these away.
I thought I would miss the lock rotation switch, but I don't at all as it's simple enough to swipe up and lock... easier even in some ways.
The battery life, is decent, but it is not nearly as good as any of my old iPads... even the iPad 2 which is what? 3 yrs old now? The battery drains while it's just sitting idle - something that never happened on any of my other iPads. With that said, I am cycling the battery now and I'm optimistic battery life will improve. It's not bad... just not to the same high standards as all of the previous iPads.
I don't mind the compromise so much on battery life as I think portability and weight of the iPad are much more critical factors than just battery life. I hope Apple can return to the same prior battery performance next gen while making the iPad even lighter. I doesn't have to get thinner... just lighter in weight.