The collision detection is horrible, the gameplay is boring, the dying screen takes far too long given how many times you'll try to jump onto the background, and the music is certainly nothing to write home about.
Great game, but the groaning vibration thing is really annoying. I keep drowning because the vibrations stop me from making underwater jumps. 4/5, would be 5 if it weren't for that.
The gameplay and music are both good, but a few flaws. For example the vocals sound terrible - it really draws attention to how compressed the music has to be for a flash game.
If your arrow keys are sticking, try a solution from here: http://www.kongregate.com/forums/7-technical-support/topics/67250-fix-for-keys-sticking-in-games-in-internet-explorer
 "Water Werks"){kind=icon}
 "Evolution"){kind=icon}
 "Heart of Ice"){kind=icon}
 "Scene of the Crime: Golden Doll"){kind=icon}
 "GunBot"){kind=icon}
 "Robot Wants Fishy"){kind=icon}
 "Heir"){kind=icon}
 "Depict1"){kind=icon}
 "Bieber Bottle Bash"){kind=icon}
 "You Have No Legs"){kind=icon}
 "e7"){kind=icon}
 "Farragomate"){kind=icon}
 "Transformice"){kind=icon}
 "Waterfalls 2"){kind=icon}
 "Zombies Took My Daughter!"){kind=icon}
 "Switch"){kind=icon}