I think the key difference is in the OS. By taking the iPhone OS and scaling it up, Apple has been able to create a vastly simpler experience built for the relative inaccuracy of touch control (compared to a mouse) which will be augmented and refined as the platform grows. The coming crop of Windows tablets are still going to try to shoehorn Windows 7 in there, which will require more hardware to run acceptably and have a hard time achieving similar battery life in that form factor. A lot of them are going to try to develop their own "interaction layer" on top of Windows 7 to try to make it more touch-friendly as well. It will be interesting to see how the coming Android tablets turn out. Just running it as the phone OS on a tablet won't be as compelling. Apple clearly put a good amount of time into rethinking their core applications and improved the experience with the larger screen of the iPad. Having nice hardware is great but without well conceived software to go with it, it's just a pretty slab of metal.