I can see the criticism here. It's not a full blown Mac by any means. It only has a slow processor (comparatively) and zero expandability. It really is just a big iPhone!
Having said all of this, I still want one! What is it about Apple that makes me want to buy everything they produce despite the inflated prices?
I think I know the answer. Apple are the best company in the world at anticipating the future desires/needs/lusts of the general public. They are also very good at understanding the importance of the human interface with the machine. This is what marks the iPhone out against other smartphones and the Mac OS against the ubiquitous 'Windows'.
The other thing that makes the iPad an interesting prospect for me is its use of 'apps'. This feature wasn't top of my list when buying an iPhone, but I've come to appreciate the app store and the many wonderful (and/or useless) things one can find. I think this will turn out to be a strenth for the iPad too.