SourceWell... well... sadly, the HD 4800 family won't be supported, because AMD thinks NGOHQ.com is not worthy enough to borrow review samples (definitely a bad idea). Anyway, expect to see some cool demo video in several days-weeks. Remember, it takes a lot of time and work to make CUDA compatible enough with Radeon to get it to fully work without any issues.
Pretty awesome if you ask me... NVIDIA wants ATI to use PhysX, so it will be interesting to see if they give in.