Oh ok, well, it's your choice.
LEFT and RIGHT controls feel sluggish, have the rodent accelerate and decelerate faster. You know these ice-blocks in lots of similar games that reduce your traction? Right now it feels like you're constantly on these. I DID get used to that after a while but it isn't very precise.
Allow the rodent to jump through the top of the screen instead of bumping against it. Not only is that the cause for many frustrating deaths, it also doesn't feel 'right' to me. Hard to explain.
If possible, try and fix the problems with getting stuck on ramps when you're not jumping and being stuck in walls when jumping into these.
There are some questionable level design decisions such as death traps in there but with additional levels that can be rectified.
Re-design the vanishing blocks so it's more obvious when they'll appear and disappear. Right now, when there's only a lower part of the block visible, you fall through them - and in general it's hard to tell if a block is appearing or disappearing. Maybe there's another design that clearly shows when the block is solid and when it isn't.
For reference, this is how Keen did it:http://www.youtube.com/watch?v=LGIDVLls1Xc
Apart from that, it's a great jump'n'run game! Very impressive and fun!