I've been using Apple's iPad Pro keyboard now a few weeks and thought I'd report in:

They are still difficult to acquire. I ordered mine at launch and it took several weeks to ship. I was in an Apple Store a few days ago and told they are still difficult to stock.
The keyboard-in-cover design has been done by third party hardware companies (and Microsoft) for some time but this the first time I've seen the keys molded into the cover. It's nicer than I expected.
The feel is alright. There's more travel than the new MacBook keyboard. I don't hate typing on it but also I've been a minimal keyboard guy for some time now.
The keyboard size seems about right. It doesn't feel cramped like some of the cover-keyboards I tried on the iPad Air. Of course, they have more room to work with on this jumbo iPad.
The sound is weird. It's louder than you'd think and doesn't sound like a typical mechanical keyboard.
The whole monkey-works is just a bit thicker than a normal Smart Cover and it includes a functional, working keyboard. It really feels like no extra weight or thickness bringing it along.
I sure would like some dedicated iPad keys but not at the expense of making the existing keys smaller. I suspect that's why we don't have them

When the iPad Pro was first announced I knew there would be a lot of third party keyboard cases and I figured the winner for me would end up being something from Logitech. However, the Apple keyboard has the right amount of balance between minimal profile and working keyboard that I think it is the keeper for me.