Totally agree. Grand Central will optimize performance in multi-core CPUs. According to Tallest Skil, those optimizations are significant enough for a dual-core CPU to beat a quad-core CPU.
Sounds like Grand Central is going to be like the PPE is for the SPE's in Cell for Apple.
I just think it is amazing that Apple would even admit that their tools sucks so much for parallelism that they have to come out with this "new" tech to help developers with it.