i liked it :)
i gave up on the bonus level due to the length but i did enjoy it.
i didn't like the level where you spawned ontop of a spike. you could try spawn the player on the platform to the right; the challenge would still remain as the player would have to fall down to collect the balloon but it'd take a lot of the frustration out of it.
other than that though it was pretty fun :)
i also liked the little decorations and the secret message in level 1. good stuff.
oh and the angry balloons reminded me of the ghost from spelunky which was cool. not really related to anything but y'know