Since shader model 6.8 contains gpu heaps module which translate's data from cpu to gpu vice versa by a low latency subset by using resizeable bar im sure , rebar will be smoother an faster. Can someone test a few titles with rebar enabled games and see how this actully holds up to the information microsoft state's.
GPU Upload Heap: This feature allows the CPU to address the entire GPU VRAM frame buffer, instead of only addressing 256mb chunks, this allows for faster data transfer between CPU and GPU. This feature requires Resizeable Bar to be enabled and supported by the PC.