I love the game, but it's MUCH too straightforward compared to usual Metroid games. The ONLY way it could be non-linear-ish is if you went the wrong way, and you're immediately greeted with an obvious road-block and a quick message to shove you in the right direction.

I liked Super Metroid's subtle use of progressive-upgrades much better. Sure, you still had the usual roadblocks like missile doors and updates of that, but you had things like areas-too-high-to-jump, grapple-beam-blocks that you didn't know what they were at first, and other neat things that you FIRST overlook, but after getting a certain item you think 'OH, I remember that place wayyyy way back there that looked like I could use THIS to get past it!!', and that was just so much cooler.
And Feu.......I LOVED the dark atmosphere...

Well, I appreciated it when I played the demo back when it was first released, and I probably didn't FULLY come to appeciate it til I played it again when I was 18-ish, but I loved it. Makes it more realistic, even for a 2D game.
Still, MP3 is a good game overall, and definately FEELS like a Wii game, rather than a Gamecube port. I know I'd get walloped for saying this on Oldsider(oh, feel the clevernesseseses), but I really think I might possibly have mistaken it for a 480p-XBox360 game if I didn't know 1000x-over that it was Nintendo. Of course, I also mean that it feels like a Wii game in its controls as well, since they actually made them GREAT, although my older brother hates them. -_-;;