I have uploaded 32bit and 64bit builds to graphicall.org that have SSE optimisation for the renderer enabled. This is not a default setting, but I thought it’d be good to get some testing results out of it – whether it causes render artifacts or not, and such.
To use any of the optimisations, check the Performance panel in render settings. The Auto setting tries to select the best optimisation strategy, but you can choose any of the other ones too. Octree is what we know from the previous Blender series, all the new names are from the GSoC work done by André Susano Pinto (jaguarandi).