I must say that I'm impressed with the atmosphere you've just provided, especially the intro. It has a depth that shouldn't be looked by and then it gets better with the introduction of more synths and pads. I felt that the piano could need some more reverb and make it distant, like echoes lost in deep space. Sorry, had to throw that in.
The structure is somewhat varied, although I would have probably expected a change at around the third minute just to keep things renewed and interesting. The outro kinda feels a little weak compared to the song, I would have introduced a fading out while gradually increasing the reverb of that synth. The given effect is that the sound gets more blurred in the distance, it's very cinematic.
But no matter, I give you props for experimenting with an enjoyable ambient piece and ultimately for your art choice which is equally beautiful.
//FD