If I were a student: I would use it in class to take notes and browse a PDF version of my books. Imagine being able to scribe notes from vector calculus on to the tablet only to have completed expressions converted to a digital font easy to read and study from? Integrated scientific calculator and graphing tools. Ad hock network connection to share notes and ideas in group study.
If I were a doctor it would be my digital patient file. I would have software which would automatically load the patents file from the central database when I walked into the exam room I would have access to all images/x-rays/scans the patient had ever received a full searchable patient history. The tablet would wirelessly integrate with my equipment allowing me to record various measurements I had to take.
The tablet would have a dock and or a kick stand for watching movies or viewing documents when a desk was available. It would use an on screen keyboard, on screen character recognition or the "laser keyboard" technology for user input.
There are thousands of places I could see where this can be used where either paper or laptops are used today in an awkward manor.
What Would You Do With An iTablet?