I didn't even pay attention to this when it was revealed as I thought it was some sort of anime thing.
I gave it a go off the back of the positive hype and was pleasantly surprised.
This feels as AAA as anything else, IMO. Very polished, great visuals, performance, animation, environment. No idea why some are saying AA. I'm not sure what could be better, given that the vision seems complete. I assume it must be quite short, given the price.
I think it's great that Microsoft let this out the door with no build up, no leaks and the result is people have tried it, and embraced it and it's now spreading organically. I assume that this release is an experiment for Microsoft and that they'll be trying various things in the future to see what works best for them and the players, both those subscribed and not.
I'll be interested to see what the reviews are like, seems to be universally liked on metacritic (aside from the obvious weirdos who pop up to slate things - this is obviously not a 0/10!).
Needless to say, a pleasant surprise.