I'm surprised no one has mentioned this in this massive thread (unless they have and I missed it), but a tablet is a perfect place to implement a shapewriting input system, where you drag a single finger over keys on a keyboard to "draw" words rather than stroke each key individually.  This would allow easy one-handed entry, something that will be crucial for a larger-format device.  The software is already available on mobile devices and Windows-based tablets via 3rd-party software, but Apple would be wise to integrate this functionality at a system level in their upcoming tablet (if indeed it exists).
	
		
			
		
		
	
				
			 
 
		 
 
		 
		 
 
		 
 
		 
 
		