The melody and progression of the piece is really fantastic, and the vocals are gorgeous.
I felt like I should nip a few stars because the whole piece sounded like it was being played in a tissue box. It almost sounds like you cut out anything below the 800hz range. The complete lack of low-mid and lower ranges makes it feel extremely tinny and wispy. I understand you were going for ethereal, but I don't think that necessarily precludes the lower ranges. A huge swell in the lower end around the 1:30 mark would have turned my spine to jell-o.
It's a really beautiful piece, and I guess I just wanted to hear it more "fully". Great work, and I look forward to hearing more from you!