A Renderman exporter won't be part of the first release of InterChange for
Windows, but it will be part of the second release. If anyone is interested in
this, they can send me their address in private mail and I'll add them to our
mailing list.
I'm sure it all depends on what you model and how you want it to look. You ask
a very general question, so I can only give a general answer. 🙂 In general,
I'll venture that it's never going to be possible to freely exchange models and
animations between renderers to get magical improvements in the "look" or
speed-ups in rendering.