Hi. I'm going to nitpick the hell out of this because there are few major things to comment on. Be warned, there will be no mercy at all. Period.
The Good:
-Intro is nice, I like that kinda little glitchy sound along with the background ambiance. Definitely not Omnisphere there right? c:
-Plenty of little details everywhere such as the little subtle drum fills in the intro.
-The buildup to 0:46 is niiiiice, the release there is great too.
-I still love those bitcrushed high-hats starting at 0:46.
-The two main melodies are very good, very nice-sounding and soothing overall, even in the 'epic' zone.
-White noise sweep leading up to 1:20 is very nice.
-I particularly like the synth arp at 1:26.
-I love the little reversed mechanical groan-like noises at about 1:52-2:05. Would they happen to be filtered bass drums?
-The overall flow of the piece is wonderful. Two nice rises and falls. Classic.
-2:50 I've said this before, but DAT CHOIR BE SEXY.
-Transitions are fine. As I said, the buildup and releases are good, the overall flow is wonderful, and the transitions get in the way not at all.
-The final climax isn't TOO short IMO, though it is a bit on the short side.
-All those effects, you really brought in the motherload this time. Where the hell did you get all of those.
-The ending is nice, I'm glad you finally brought back that piano riff.
The Not-So-Good:
-Unfortunately, by 0:46 that hit is getting a tad bit overused, awesome as it is. Also by about 0:46, it would have been lovely if there were some melodic development. Y'know, not just the atmosphere (as nice as it is).
-The release on the Cryogenic Freeze pad is a tad quick and sharp at 0:51-0:54 for my tastes. It just dies VERY quickly. After that, I do like how it builds up in the background. However, it would have been nice if the release were extended a little bit.
-There is very little melodic development at all. While I understand that this is meant to be more ambient, that doesn't mean there can't be melodic and thematic development. Ambient is NOT solely about atmosphere.
-The electronic synth that comes in at 1:08 gets off-key in the background at 1:18.
-YOU USED THE EFFECT AGAIN AT 1:20 AND 1:42. Effects are nice, but one thing to remember is not to go overboard with them.
-In the climaxes, the mixing sometimes overpowers other elements, such as the bitcrushed high-hats during 1:20-1:42. They're fairly underneath the rest of the mix, only barely coming out mainly when they're allowed into the high end of the chat.
-I also notice about the synth arp which I said I like (at 1:26 and other places) that it has a bit of a lead-in sound, which almost sounds like a mistake.
-Stop using that effect everywhere. You're using it like you used to use cymbal rolls. Just. Stahp.
-The spiccato strings at 2:05-2:25 sound very quantized and inhuman.
-Now for something I don't normally say - more advanced composition theory. The melodies from about 2:05-2:50 are disconnected from the other parts of the music. They are simply filler - lead-ins for the rest. Before that, there was a decrease in tension which works. However, beyond 2:05 there should be *something*.
-johnfn is absolutely right. In the second climax there's even more drowning-out of other instruments, particularly the bass. But overall, the mix is just plain stressed and I can barely hear any of the effects and stuff. You say I have a muddy mix sometimes where instruments are drowned out, but holy crap man. Talk about the pot calling the kettle black!
Overall: Great ideas, spectacular ambiance and atmosphere, flow is spot-on. On the other hand, there are some mixing problems, you obtained a replacement for your cymbal roll, and there's extremely little melodic development. As far as I can hear, there are precisely two points where each main melody is played, and the rest of it is filler as far as composition goes. You did a spectacular job, but you CAN do better. Ecosystem was far more impressive in terms of composition, though when it comes to atmosphere and effects it loses by far.
Good luck!