I've been playing through it, and I love it. The physics are very simular to Metroid 1, in terms of falling and jumping. You can't wall-jump untill you find the item that lets you do so. The map layout is COMPLETELY original, not a shred of the original map at all.
I'm already in Brinstar, and I have yet to find a Energy tank. Only have 7 missles, morph ball, and the wall-jump boots.
There are some definite "Oh SHIT!" moments. No spoilers.
I'm a bigger X-Strike fan than you.