zionner, Lucio,
I don't want to release any benchmarks at this stage, but early testing shows that the multi-threading gives speedups on 2 cores and on 4 cores that are very reasonable for some scenes. It remains to be seen how well this applies to a wide range of scenes, especially more complex ones, so it would be foolish to give any figures just yet. Global illumination and other parts of the renderer have also been optimised and now render more quickly, especially at higher detail or resolution. Work is still being completed on the ray tracer (which is a big factor in render times with reflections or detailed GI), so I can't give any more information about that just yet.
Matt