Looking good, the only thing I'd alter is the neck to be a bit thicker at the bad, otherwise there isn't enough internal space for the impusle engines to occupy. I think you'll find it improves the look when viewed from behind as well.
The general placement of parts seems spot on, I spent quite alot of time tweaking the placements of parts so the ship would look good from as many angles as possable. The Bussards are designed so that they have partial forward visability (each nacelle has one entry point with full forward exposure).
The bridge area seems a bit off. I think the deck area under the bridge needs to be slightly larger.
The aft torpedo launcher is above the shuttle bay at the end of the spine (similar to the Galaxy class) so you might want to model it in there.
Other than those minor details, shes looking really nice, can't wait to see how you texture her. I used Galaxy class style textures on my renders since she is meant to of been developed between the Ambassador and Galaxy class, although its worth noting she is a light cruiser, not a heavy cruiser. I updated the blog page linked earlier in the thread with some more images btw.
Keep up the good work :-)
