Haven't written a review in a while now... Hope I still remember how it's done. ;D
So, from the top: the intro with the clean guitar felt really good, even though the progression seemed awfully familiar to me. The sound of the guitar was pretty nice, and had just the right amount of reverb. Then came the short synths (premiering at 0:32). They sounded a tad too slow for me, which could possibly be helped with reducing the Attack of the soundfont you used, but what I would really suggest is layering some pizzicato strings above it, perhaps with just a pinch of delay, just to accentuate them a bit more. Then again- that's just me. If I could, I'd throw in pizzicato strings into grindcore, so yeah...
The deeper section of the same strings sounded well because the melody was more connected (without the breaks), so the slow attack wasn't that noticeable. As for the piano coming in at 1:29, I truly recommend you either plaster that bugger with some massive reverb, or even better: give it a slow delay, just to reduce the cut-out feel.
The section following this one sounded well because the bass helped round all of the instruments in a nice, wholesome section. I must admit that the sound of the guitar was slightly less-then-satisfying, but soundfonts are always a bitch. Sad fact, but it can't be changed. However, the same lack of attack (I'm rhyming, yay!) that I mentioned for the short strings can be applied to the guitar in section starting at 1:51. The pauses and the sound that the guitar makes when it comes in just don't sound natural. Possibly layering the section with another guitar might help.
The cymbal at 2:11 sounded waaaay to artificial, so I'd say take a minute or two and toy with the volume and panning for each of the individual crash hits, jsut to soften that computerized feel. Also, I'd personally go with less crash hits in that section: if it's all 8th notes, cut it down to half the number of 4th notes.
The section at 2:32 was really a thing of beauty. The instruments just blended in so nicely, it was really darn awesome. Still, the sound of the quicker guitar notes could be improved, once again, with some layering. The rest, with all the strings, almost brought a tear to my eye. Really, really touching.
Then the sudden ambient sounds/noises came in, and I have to say that they really surprised me. Didn't see those coming at all, and they made a very nice addition to the song. The whole section was excellent, except for a single dissonant synth string at 4:21. That one really pinched my ears. :P
I hope you find these observations at least a tad helpful. This song has some serious potential, but it needs to be chiseled into shape for a little longer before it can maximize it. Keeping my fingers crossed for your success on that. ;)