Hi Mark, I indeed stumble into a lot of frustration with this issue.
Milkshake didn't work for me, maybe I did something wrong in the export?.

Rhino appeared to do it right but as far as I could see the material definition were not read.

I ran into similar troubles trying to UV unwrap more complex models, the vertex normal are often lost.
I found a small trick.

1-export the model from MOI
2-Open with a 3d program and do the unwrapping. (This is one thing blender is quite good at)
3- Same the obj under another name, it will most probably have lost vertex normal info.
4-Open original Moi export with uvmapper and load the uvs from the other obj file (from file/import Uvs..)
5-Save the file.

This way you have preserved the vertex normal and have your Uvmapping.
Zbrush recently had a nice uwrapping plugin also


Michael, it would be very convenient to have such an utility to merge obj. files.
I'm sure a quite a few users will find it useful.

If it's a simple thing to do, I think it might be a simpler solution than integrating a export/meshing/layering/ mechanism inside.
Thanks a lot for your support.

Marc