So this is a WIP. So, when I review this, I was going to evaluate the current WIP as it stands (almost like it's a finished piece. Keyword, almost.) and then discuss how a potential final rendition would fare. So let's kick things off with the instrument choice.
The instruments in the beginning sound good. That 'wind' sounding synth right before the dubstep section is pretty good too. All your instruments in said dubstep section are pleasant to the ears as well. I gotta say, the instruments are sounding great: The percussion sound good, the synths and pads sound like long, lost lovers together (which is a good thing!), and the 'dubstep' (I kinda suck at describing dubstep instruments' sounds) parts of your piece sound absolutely great. I'm loving the dubstep a lot.
As for the mixing, The instrument that plays your chords in the chorus seems a little loud, and overpowers some of the rest of the mix, especially around the minute mark. In addition, I feel like your kick could be given a slight volume increase. I can *just* hear it over everything else. Other than that, the mixing is actually pretty good. You say it'll be a pain in the ass in the final version, but that pain in the ass will really pay off if done right.
Composition-wise, it's pretty darn good but of course, since it's a WIP, there are some hiccups. I don't hear much of a drop after your build-up. It just seems to go right into the dubstep. If there is a drop, it could benefit from being more pronounced. The build-up isn't as lame as you say but it does need to be fleshed out a little for the final product. I like the rest of it though. It's headed in the right direction for sure!
For the feel and theme of the piece, there isn't much to say since it's unfinished. The instruments work well together to create the same feeling throughout the piece. In a few words, the theme and feel is really nice!
Overall, I think this piece has potential to be a really good dubstep piece. For a finished product, I would expect: the mixing levels to be perfected from what I hear here, the few hiccups here fixed, and all the great stuff the song has going for it to remain unchanged for the final version (I'm talking the instrument sound and the overall feel of the piece.) Your dubstep composition skills are great and the song is a strong start for a WIP. Let me know when the final version is released. I would like review the final version to see if it has improved upon the WIP in a way that makes it stand out as a great song.