I enjoyed it. I can see some people finding it a bit frustrating, but it's my kind of game. I love physics based platforming, and I thought the level design was pretty clever (though it could've been more forgiving). Good choice of music as well, it's a must to have something with a slow tempo when the game demands patience. It added to the atmosphere a lot as well, I'm glad you guys chose to publish the game with music.
As for things that could make the game more fun, I immediately think of an arc direction indicator, and a way to control the strength of the jump. I have no idea how hard those would be to implement though, and I think the game is fine for what it is anyway.