http://www.blender.org/development/release-logs/blender-250/sculpt-and-multiresolution/ Release logs are work in progress, also check missing items on that page, there's still a few things that need work. Quick summary of the changes: * Use BVH for optimizing sculpt mode, doing only editing and updates on nearby nodes. * Memory reduction by use of CCG grids for subsurf, own undo stack, no vertex-face map, no origindex, .. . * Multithreading for sculpting, multires, and subsurf. * Optional external file storage for multires displacements. * Various tweaks to brush behavior.