Pretty good game.
What's with all the people giving either 10's or 0's?
You've got a pretty good game here. At least I found it pretty addictive, though I can definitely see how it would get pretty frustrating.
My first suggestion is that you work on graphics. That dull gray gets pretty boring pretty quickly. Things don't have to be bright and cheerful, but even just a little brown would really help. I would suggest making some simple backgrounds, maybe a few different gradients blended together and blurry, and perhaps having the background change every level, or every few levels. Maybe a distinct progression from one color to the next as the game goes on or something.
Also, you could play around with difficulty levels. Maybe make an easy mode where the bouncy balls move slowly and the game ends after level 10, etc. For future games, choosing differently sized playing areas could prove interesting.