Well...pretty good
It's not a bad engine...the problem is it just needs more. The levels need more than just a track, and there needs to be more levels overall, rather than three levels over and over again with smaller times. The problem with that is that one each level I was well under 10 seconds beneath the time to beat on the first go. Therefore a few seconds shaved off here and there really wasn't changing much.
The last thing I think should be different is the HUD. The odd shaped blobs block parts of the track that I really need to see. I think if you want a unique HUD it's okay to have it sort of like that, but make the blobs smaller and less intrusive in the view.
The good parts were the graphics, the music, and the physics. Those were all very nicely done.