I first heard about Bloom from some co-workers when we were exchanging App ideas. I heard Brian Eno was involved with it and became very interested. I like some of his early work, especially Ambient 1: Music for Airports.
The program doesn't take any musical talent to play (although it might help some). You just pluck the screen where-ever and whenever and hear some ambient tones. The tones are almost like wind chimes, not quite piano, rather synth-y. There's an ever-present underlying Eno-esque score of light synth playing which is nice. The notes evolve over time if you leave them alone.
At $4 it's not going to break the bank but it might be on the pricey end of the scale for what it does. Overall I'm pleased I have it and play it every once in a while to zone out.