Excellent game - certainly well among the best Flash rhythm games I've seen. But... may I humbly request that the hammer-ons and pull-offs be made more obvious? Sometimes it's a little difficult to tell. Many people reading this comment likely didn't even know that they were implemented.
Unless I'm mistaken, there is no reason at all to repair your car. The only thing that happens to a damaged car is that you lose points... which do nothing. It would be wiser to just use the cash for upgrades. If you're concerned about getting a high score, wait until you have all the upgrades, at which point money won't matter, so you can repair away.
Eh. Sort of like a watered-down Pwong. My main issue is that sometimes it's just undoable due to the random projectile motion; if two balls happen to land on opposite sides at the same time, you're sunk.