maybe you have noticed great news bout Matt Ebb’s new addon. 3Delight external render engine exporter for Blender 2.5. More details here:
3Delight is great and fast renderman compliant render. Used for example in Harry Potter or X-men films. Moreover it is free even for commercial use (with some little limitations).
Unfortunately I have problems to apply addon and it (Windows 7). What are your experiences?