How many people ONLY have a tablet and not a PC/Mac/notebook. Hands up out there.
Well that is not many. The post PC world is still driven by the PC in one form or another. Would anyone seriously write a book on a tablet, even with a bluetooth keyboard attached? How about do serious video editing, audio editing, desktop publishing? What on a 10" screen? Even accounting. The time will come when you can sit you tablet down next to an external large screen, keyboard with extra USB3 connections and HiFi speakers and it will all automatically sync together and become ..... a PC. You can then pick it up and walk away with it until your significant others shout "who has taken the PC?", then you will need a second tablet to supplement your err PC.
I have a PC, a notebook and a Xoom and a Samsung Galaxy S - they all share calendar, email, docs via the cloud and they all work in harmony. And they all have their purposes. The only real redundancy is that the notebook could replace the desktop, but not if the tablet replaced the notebook.