Well to Apple it was either an giant iPhone or just a giant touch screen with Mac OS X. With the Mac OS X option, nothing new would really appear and since theyre always to top their last product they had to incorporate something new. This is where the giant iPhone idea came along. They took the concept of a tablet and an eBook into one. Of course like all other Apple products that were successors of others emulation is possible. (like PowerPC and Intel Processors; PowerPC emulation with Rosetta on an Intel processor) So you can still use iPhone apps in full screen.
But again its just a giant iPhone.... I MEAN IT GETS 3G HOW MUCH MORE OF SIMILARITY DO YOU WANT?!?! rofl and try holding that up to your ear.... *drops; $500 ripoff breaks; you start crying*
~ Jon