First, check out the cool launch trailer: http://www.gametrailers.com/player/38442.html
Anyway, I've put a few hours into it so far, and I'm very happy. It's hard, but in the way that makes you want to keep trying rather than simply throw the controller through the TV. And the music is awesome. When I first saw the slime enemies in the sewer level, I suddenly remembered being huddled over my Fat Boy back around Xmas 92. I grew up with the [arguably superior] GB version, not the NES version, so that has always has been the gold standard for me, and this release takes me back.
I only have two criticisms so far: the save system is confusing (it says if you quit it you'll lose unsaved progress, but then after you quit it says it's saving... so is it recording your progress or not?) and I wish it wasn't so hard to do the drop/rehook manuever (you have to push down on the d-pad to drop and then release down immediately so that when you hook it goes diagonally instead of straight out) though at least they give you a way around this once you get the shotgun.
Anyway, I'm having a great time, and I love how the bosses actually require some thinking to kill. You can really tell the guys at GRIN loved making this game. From the large number of secrets to the massive amount of details in the animations to the variety of ways to get through each area to the killer remixed tunes to the campy 80's dialogue, there's plenty of awesomeness to go around. It's such a shame that many people will write it off after playing the demo and realizing that Radd can't jump.