I can see your point, that was want I wanted too, but the more I thought about it, I thought about this:
The Mac OS X was built for the mouse and the pointer. Would you think it'll be practical to use your everyday apps you use on your mac with a touchscreen? That was the problem with Tablet PC with Windows.
With the iPhone OS esque interface however, it's way more intuitive and natural. However, I do agree with you that there should be SD/USB ports for easy file transfer without a computer, iSight, handwriting, multitasking, video out, etc.
Basically a more open system with 3rd party apps without the app store, a central file storage system like the mac, etc.