One advantage over seperate dual processors is having everything on board. Anytime you don't have to go off chip you have quite a bit of speed advantage.

Software would have to be changed to take advantage of this. One use would be multiple threads for programs and operating systems. Programs could run on one core and the OS on the other. Or tasks could be divided between them.

Controlling this should be much simpler with it all being on chip. Of course, Intel will probably screw it up. :)