I went with the leather Smart Cover and sleeve.
Then I bought the Logitech keys to go (which I keep in my bag) and the k380, which is nicer and I use at home.
I like the 12.9 more as a tablet, so good transport/being able to hold it more comfortably suits me more.
I had the keyboard for the first gen, and holding it was pretty awkward. I tended to keep it off and at home.