Wow! I must say... and I hope you'll forgive me... that I was rather disappointed with the final image. :-| I just saw the thumbnail (looked good) and headed straight to the YouTube "making of"; it was interesting to see you work, see the progress from the initial sketch (I must admit I skipped now and then because 3.5 hours is a long time ^^)... But surprisingly, I like the final image much less than the W.I.P. version!
So as to make this comment a bit more on the constructive side, I should say that the day setting you seemed to plan at first was a better idea than this odd "smokey night" mood. Besides it seems you got rid of most of the initial buildings, or lost them in the chaotic scenery. The fire/explosions seem a bit lazy too, they didn't benefit from the same effort of photorealism as the characters. Eventually, I think what weakens this artwork is the very scattered shading of the bad-ass alien-cyborg guy. Too many light sources and shadows, so it lacks a solid light that would improve the volumes.
That's about it... Then, that being said, I think you're a great artist who keeps getting better with each new artwork, so keep up the good work! I just felt I had to tell you what a let down it was to find out the unfinished pic looked better (to me) than the polished, final version. x)