If a tablet does materialise, what will make it successful? Being large enough that reading web pages is not a chore, but small enough to be easily held in one

If a tablet does materialise, what will make it successful? Being large enough that reading web pages is not a chore, but small enough to be easily held in one hand and poked at with the other. Many (, many...) elaborations come to mind, but thats the minimum viable product. Its kind of amazing that tablets haven't been more successful. Unless you are actively editing text (not the norm on the web), that keyboard is just there to prop your laptop monitor up at an appropriate angle. And the mouse? Cocoa Touch has made that seem pretty silly outside of pixel editing.