I think its really fun, the only real complaint i have is the... erm, what do you call it? Pistons? Basically, the pillars that move up and down. They don't really emphasize speed running when they involve waiting for you to pass through them.
The best thing about this game is the anxiety you get. When you fall all the way down, it can be kind of scary. but that's a good thing, it gives me the feeling of the Foddian genre.