The concept is way over used, you should take the concept and throw in a little "twist" so it's original. I do like the graphics though (because it is sort of cartoony) and you don't see many games like this with those types of graphics.
I like the game, I have some suggestions (not necessities, but I'd like to see it) Color changes, so people can change the color of the ball and paddles/rackets, a 1P mode, make the ball start out slower instead of rocketing towards P1, after about a minute of noone scoring the ball should go faster, and that's all my suggestions...
Just some constructive criticism....
But the box moves way to slow, it takes like 30seconds to get it out of the way. I would make a few more levels before posting the beta (but maybe thats just me), Being able to jump an unlimited amount of times in a row makes the game to easy, when you die nothing happens even after you lose all lifes, you should say they have to jump on the coin to get it, they shouldnt be able to just walk through because when you get to 1 of the places where you should need jump it just puts you on the top, when you fall it doesnt hurt/kill you, and the text doesnt really match the looks of the game I would try using a font like Cosmic Sans (it's more...doodley?)
I like the doodle background, the little blocks for like land and clouds to walk on, the enemy movement, and the little climbing rope, this is better than what I've posted here...i lost my adobe to a virus :/
I like that. You smart son.