I chose not to round the engines, because I like the octagaonal look. I might go back and round them anyway, though. I'm seriously considering rebuilding the forward hull from scratch so that I can maintain the smoothness better. Because a lot of the way I work is point and poly tweaking, smooth surfaces get creased, and there's only so much you can do to clean that up without rebuilding the piece from scratch using the finalized shapes.
Karma, the Nebulon-B is one of my favorite models, but I have reservations about working on it (or any other Star Wars model--indeed, most any canonical model for anything): there are certain expectations the audience has about a canon ship, so there's only so far you can tweak it before it becomes something else.