I'm very new to Android, and I'm curious as to what separates TouchWiz from the stock Android and other overlays such as Sense. My only experience with Android so far is with this new Vibrant, so I know no other. Is it the specific apps that makes up the overlay (TouchWiz)? I keep reading that TouchWiz also comprises that actual UI. How would the stock UI be much different? Maybe I should re-phrase the question in terms of what is common to all Android phones besides the obvious Marketplace?