The new 3D PaintBrush app Ralf mentions above seems pretty good! (http://www.3dpaintbrush.com/)

Introductory price = $99

The UI seems nice and actually easy to use.

It can load a 3DM file directly but it does not seem to do a very good job of producing a mesh directly from the NURBS data, but bringing in OBJ files exported from MoI seems to work well with it. It appears to load in all the vertex normals and material information from OBJ files so that is great.

This may end up being the kind of missing link for an inexpensive but easy to use standalone rendering program.

It may possibly be a little too streamlined though, there does not seem to be very many options exposed for tweaking the rendering like anti-aliasing settings, etc... but it seems like you can get a basic result quite easily. I wish there was an option in it to adjust the view rotation to keep the same "upwards" direction while rotating around though.

I would think this would actually go somewhere near the top of the list to check out for getting stuff done easily.

- Michael