I don't like to tell a lot of people, but if my hairy knuckles are any indication...
So far, this is really good. I'm not gonna spoil stuff, but let me just say that this is a Metroid fan's Metroid. At least from my initial 90 minute impressions. Once you get the parry mechanic down, it's really satisfying. I haven't fought any bosses yet, but I have about 9% of the map filled in. I'm not very far at all. There are a few subtle mechanical changes that fans of the 2D games will notice, but I'm hoping this game will go on to become it's own thing, and not be compared so much with other 2D Metroids, cause the 3rd dimension, and all-direction aiming really make it feel like a different style. As far as comparing it to AM2R, well, it's hard to say so far.