I guess the categorisation thing is nothing new and depends entirely on where you position any given 'Pad' now.
Historically we had:
- "tablet PC's" (PC's) (failures ... but yeah, Apple did not 'invent' this category with the iPad
- "portable media players" e.g. the 7+ inch Archos offerings etc.
Unsurprisingly the iPad falls somewhere in between the 2 running the OS of a mobile device (effectively an oversized iTouch) -- but featuring App platform capabilities not generally seen in personal media players like Archos historically.
Personally I think the iPad is more in the mould of a PMP and Apple gives this away with it running iOS as the OS and doing everything through their media centric iTunes ... if they moved towards running full OS/X (as some of the Win 7 tablets are doing), then I would definitely count it as a PC. Likewise ... Android tablets as a PCs ??? ... Nah!
How can you take a clearly mobile platform and blow up its form factor and call it a PC?