First thoughts: you've gotten a little too close to the sweep button. Also, turn off quadrangle subdivision if you have it on, thouse are fine for renders but terrible for FS models. I wouldn't mention it but it looks like (particularly on this design) that there are a couple of areas comsuming the vast majority of your polygon count, i.e. the leading edge of the forward "wings," and they have a bit of that repetition indicative of the quad division feature.
The design is good, much better than my early designs. Just try some things besides sweeping, or sweeping different parts in sequence, rather than relying on one long sweep to get you where you want to go with extrusions. Not to discourage you from using the feature (I still use it predominantly in the construction of new ship designs), but try to make use of the bevel, tip, vertex weld, and add/remove faces tools while you are adding features. One last tip, in case you haven't been warned already, AVOID THE BOOLEANS!!! At least unless you know how to fix the stuff that they screw up...
