(Comment+props) Really learned a lot from this. Especially "glossy over bump" to produce internal refraction - works like a charm but is certainly non-intuitive.
One note: I started with an empty .blend file, added a mesh, and tried the dispersion technique; wasn't getting anything to happen. Then I noticed the mesh dimensions (quite small) in the example file. Scaled down my mesh greatly to 0.1-0.2 BU range, and voila. Apparently [node scale] x [mesh max dimension] must be around 2.0.
