I think a renderer should be last on the todo list.
A few general export formats to get your model into a package of choice for rendering/surfacing/animation are really all thats needed at the moment.
I just would be happy with a feature that hides or fades the construction lines for now... just to be able to preview a clean smooth shaded model.

+ loading background images into the views would be great too..... i can almost not do without them :)

cheers!