I'd echo the sentiments of the other reviews here about the slippery controls.
There were plenty of times I felt like I should have been in the right position to hit the target - but wasn't - or required a tiny micro adjustment and ended up overshooting it.
If I were looking to improve this I'd maybe think about locking the player to a number of discrete 'lanes' and letting a single tap side-step you between them.
Other than that the graphics and audio were fine. I also agree you could look into using something other than the default font just for polish.
There are plenty of indie font makers out there that have both paid-for and free versions of their fonts. I really like SomePx or ChevyRay's pixel font packs.