Something very interesting when you're looking for render speed: the RT2 render plugin (there's a Max version). RT2 doesn't render on the CPU, it renders on the graphics processor, and is MUCH faster than any CPU based render engine.
One of the things that I'm trying to get tested at work is how the RT2 render engine works on dual graphics cards (SLI / Crossfire). We have machines with dual 7950GX2 cards (thats 4 fast GPUs in a single machine!), and I expect RT2 to be at least 100 times as fast as MR with similar settings on such a setup.
I do not know whether the RT2 render engine can render with the quality you want. But if it does, I guess it would be a great asset to animators.

On a side note, I'd really love to see a standalone Renderman-compliant renderer that renders on a GPU using OpenGL / HLSL shaders. Preferably as an open source project.

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