Drac,

Clean lines, styling flows, creased edges blend well with the curves of the main hull.  Everything works well, except, as muse says, the back thrusters.  They don't seem to stylisticly match the front ones and that's kind of distracting... try matching the flaring from the front housing on the back and duplicate (within reason) the breaks between the hull, joint, and the engine itself (does that make sense???).  That might be what it is... there is some disparity there...

EDIT:  See attached image... I drew lines to show the corresponding change areas that I would make.

Top and rear views (quick and dirty is fine) would help in determining what seems slightly off..

Otherwise, it's a fine example of what I've come to expect from you... sci-fi art-deco (robby being the prime example).

Ken