Been playing on alpha and it's real disappointing so far. The GCD changes make a lot of classes feel really slow, and since they didn't change most classes, the removal of legendaries & tier, along with some classes just having the artifact ability removed entirely (boomkin??) make you feel super weak.
I get that you are supposed to basically be starting from scratch at the beginning of an expansion, so feeling weak should be expected, but it's a really big change in the feel and pace of the game. So far it has not been fun at all. And right now azerite gear is only giving passive shit, so I'm not all that optimistic that it will get a lot better.
Will have to see what they add, but I feel like there is a lot more than 4 months worth of work to be done for BFA to be ready (in a half decent state at least). I guess we'll find out.