Sounds cheap :P
The piano sounds very synthesized. Try adding reverb or something, man...this is an ambient song, after all. And where's the bass? This sounds very incomplete.
- Add some effects, like reverb and filtering, to the piano.
- Put some variation in the piano melody! It got very monotonous.
- Needs, NEEDS a bassline.
- The rain cuts in and out way too quickly, it's jarring.
Just some constructive criticism. :)