It was pretty good, to say the least. Good concept, a not often explored genre.
Personally, however, I think it could be a lot more streamlined. First and foremost, I noticed I didn't really have much control over my character beyond jumping. In a situation where you have to either avoid or kill monsters, I'd have liked some ability to move left and right. Plus, a varying jump height: most of my deaths resulted from overshooting a jump or having the jump not respond in time.
Otherwise, it's a fairly good timekiller, but I think just moves a bit too slow and uncontrolled for me.