Just spend hours on material-mapping an entire part library with per-face material mapping: Plywood edges and plywood surfaces. Everything looks great, but when I copy the parts into a new rhino file, the edge (per face-mapping) material is not copied. So the part gets the birch surface material on all edges.
Very frustrating.
The materials with bitmap textures are in the file, so it is not because the materials are not linked. They have exactly the same material library.