Managed to complete 1.6x, 1.7x always gets me in the middle... The concept behind this game is brilliant and I can imagine there are many songs that would perfectly fit in there too.
The increase of difficulty by speeding up the whole thing more and more works fine at the begining, but the faster you get, the more frustrating it gets if you can't keep up. So if you ever plan to make a sequel to this, it would be nice if there is not only an increase in speed, but also in complexity.
But for now, very nice and addictive game.