As I laid out my arguments in part 1, I believe the iPhone OS will form the backbone of the Apple Tablet. What is more is it will likely be able to run the same apps from the iPhone App store.
That does not mean the 10 inch screen will have 480x320 resolution. Rather that apps made with Interface Builder in the iPhone SDK can work with relative resolution independence. Switching from portrait to landscape mode provides the best proof for that. Most apps like games will need a higher res version but that should be a minor development problem.
The biggest paradigm of the interface will be wether Apple will allow more than one app to launch at any one time. Actually, the current problem with the approach Apple has taken with the iPhone is not that background apps are not allowed. Its the speed of app switching and the fact that most apps do not return to the same position when relaunched. The iPhone 3GS addresses most of the first problem. The tablet hardware will likely eliminate that problem completely. However apple and the developers need to work harder on making an App relaunch in the same state it closes.
Here is how background apps can be easily enabled. The double click home will leave the current app in the background while simultaneously going to the home screen. The running app will be represented with a blue dot. Apple may also move all apps currently running in the dock, so they are not spread out amongst different home-screens.
An alternative is to use the multi touch trackpad gestures on Macbook Pros. Swiping 4 fingers up will leave the current app running while going to the home screen. Swiping 4 fingers down may launch expose for easy app switching.
The second question is what will be the default hand held position: portrait or landscape? Most people assume a tablet to be used in landscape along with a pen. There is one small problem for Apple with that approach: the virtual keyboard. The best way to type on a virtual keyboard is with two thumbs. Holding it sideways will make some buttons unreachable. The tablet is just way to wide for that. However, holding it in portrait mode might feel just right.
Given that both the iPhone and Apple Table will be used with fingers and feature similarly looking OS, most visual elements will likely remain the same size on both devices. So the Apple Tablet will not have 16 icons per home scree plus 4 in the dock but as much as 70 icons per home screen plus 7 in the dock.