Got my 12.9 2nd gen last Thursday, and just got the ASK today after being curious about it after a few days...
It definitely is a different feeling for me and surprisingly useful. Before I got the 12.9 I was mostly using my MBP since it is so stable on a bed, sitting upright at a desk, etc. My Air2 was relegated mostly to in bag/on the go handheld use...
The ASK brings that functionality to my 12.9 IPad Pro while keeping some of that ability to hold like a proper tablet. I bought it thinking I'd return it in a few days after trying it out but of course in typical Apple fashion I'm gonna end up keeping it.
After picking up the keyboard I stopped by the Microsoft store and checked out the surface pro, pretty cool kit. But now the ASK + 12.9 Pro gives me that experience while keeping a lot of iOS functionality. I'm sold , its a must buy.