At first the character's speed seems a bit too fast but you really become adapted to it when you realize this is slightly a fast-paced game and you're tackling lots of enemies on each side all at once. What's funny is that there's actually at least one speed boost item in each level that makes you go even faster (it's purpose seems to be for making longer ranged jumps and also blasting by some enemies).
I did see "Thaddeus" credited at the end of the game as one of the sprite/pixel artists. Good stuff, really liked a lot of the monsters, bosses, etc.
I was told by one of the developers on youtube that they're making an additional Parasitus game that is going to be a prologue to this one. It's supposed to be out maybe by next week and it's gonna be 80 microsoft points (just $1). I think that's a great idea because I think a lot of people missed out on the main game and if they see this new release it may draw more attention to the original one. Plus it's good news for those that like Parasitus and want more of it

Oh yeah, I was also told that the soundtrack to the game may see some form of public release. I really liked the music and was inquiring if they'd have it available in mp3 format. If I find out any more information I'll be sure to post it here.