Just picked it up last night, I'm an hour into it. First impressions:

-Wow, the aiming is AMAZING, it really works well with Prime especially with all the scanning and looking around you do.

-The satidsfaction of shooting your standard blaster is kind of bleh, the Prime standard shooting combat is showing its age. I'm sure I'll be changing my mind as I find the new weapons though :D

-The grappling hook and other motion gestures you have to do (switches, etc.) are unbelievable. Really cool integration and it doesn't feel tacked on or anything. One of the first set of motion controls on the Wii that feels tailor made for the game. I mean its almost as if they had Metroid in mind when they designed the Wii controller.

-The (-) button for the visor switching took me some getting used to but it became second nature after a while.

-Did I mention this baby looks amazing? Easily the best looking Wii game and being a PS3 and 360 owner, I can say with confidence that visually, this is truly Nintendo's first next-gen game. Not for once did I think I was playing a GameCube game. You'll pop this thing in and wonder why the hell no other Wii game even comes close to MP3. That being said 480p looks phenomenal, nearly indistinguishable from 720p as everything is moving so fluid and fast. Everything from the character models, to level design and particle effects are astounding. Just wait til you see the interior of Samus' ship. Very nice.

-This game really needs multiplayer. Hunters on the DS had it. There is no reason (especially after all the delays) that they could not have even just tacked it on. Just the hour I played had some level sections that begged to be put into a deathmatch mode. Where's the love, Nintendo? I hate double dipping, but hopefully we'll see a Online only Metroid or something. The controls and visual design beg for it.

amen