Here you go!
Let me first state that I have never been a real fan of ambient music. I will do my best to not let this skew my review, but it is possible it could. So keep that in mind :)
Intro & Build (0:00-1:18) - This is a real slow, quiet introduction and buildup, as is expected in ambient pieces. Overall I feel it could've been made a bit quicker and a bit less listless feeling, but as I said, ambient isn't really my thing. The pace of adding in the instruments feels about right, though, so maybe speeding things up isn't the best idea. Maybe experiment with that? I dunno. Anyway, by the time the piano comes in the intro and build are really over, and the body gets started, I feel, which means that this is an exceptionally long intro and build lasting over a minute! So maybe cut it back about ten or fifteen seconds just to keep it a bit more interesting? Two points for being technically sound and decently good at its introductory and build role, however I docked it a point for being perhaps a tad too long. (2/3)
Body (1:18-3:14) - Another exceptionally long segment! Perhaps ambient is just supposed to be a bit drawn out? At any rate, this is pretty thoughtfully put together, and the melody of the piano is soothing, even if it does advance at about the pace of a waltz (tad too slow for me, generally :p). There's a lot of variation in here, though, which really helps keep the monotony down and the replayability of the track high. It's a very technically sound, if too slow for my own pace, body segment. Again very long, but perhaps not as bad a thing here as in the intro. (3/3)
Outro and Recombination (3:14-4:44) - Bringing back a bit of the drums and such, then taking them out, really helps give the song a bit of a flavor, I think. It's like it could go on and on, which it does, with the exact same theme for four minutes straight, but doesn't really get old due to subtle variation and additions. This section is again rather long, but it has a little more to do than the intro - it had to recombine the intro's drumline with the body's piano melody, a difficult task to be sure. At any rate, it succeeds, and remains short. Uncharacteristically short for the job it does with the pacing of the rest of the piece, in fact. Lengthen this if you leave the rest of the song as-is by perhaps 15 to 30 seconds. (2.5/3) Lost half a point for being too short comparatively, otherwise completely technically sound.
As for the "do I like it" point... well, I'd be driven mad if I had to play team fortress 2 listening to this, but as an ambient track, I do like it quite a bit. Not quite enough to make it to my downloaded music folder, but certainly enough to give it high marks. Things to improve is that the intro is either too long, or the outro is too short. One of those needs lengthening or shortening, I believe. At any rate, your total score combined was 8.5/10, factoring in the "do I like it" point. That nets you a 4 - there is room for improvement, but not a lot. Then again, as I said, ambient's never really been my genre, so take all that with a grain of salt, as the saying goes.
4'd.