Sweet game
I've been playing the crap out of this since I first saw it on the front page.
Graphics are superb, sound is great, control feels great (I know, the whole jump button thing is a little weird, but it takes like, 3 seconds to get used to it.)
I only have a few small complaints:
1. Make a config menu, so I can disable the music (the music is great, but I perfer to blast winamp on ocassion).
2. I love the upgrades -- I'd love to see more of them. The flame thrower needs work, it's only useful on the maggots that form 2 throws at you (enough to get the laser upgrade)
3. Put some secrets in there! I played a few extra times and was able to beat it without being hit once and max weapons. I was hoping I'd get something extra out of it :P