Sure, the iPad's got a much larger screen, and a faster processor, and even 3G, but it's just a bigger iPod Touch.
The killer application for the iPhone, was in fact, its ability to fit right into your pocket. Can you see yourself grabbing an iPad while you dash out your front door? Not me. It's big. And I already have my notebook, which also happens to be a MacBook Pro. Sure, call me an Apple fanboy, I don't care. My main desktop is in fact, a custom built PC. But even someone like me who has an Apple product, I can't vouch for the iPad.
The most critical point about the iPad, is the fact that it can't multi-task. Like the iPod Touch and the iPhone, it can only run one application at any given time. Despite having a powerful CPU on the inside, the iPad is crippled because of its operating system, the same operating system behind the iPhone. Fundamentally, if you already have a notebook and an iPhone, the iPad will have a difficult time finding a place in your daily routine.
Here's the deal: from now on, if you need another euphemism for menstruation, you can say "She's switching to Apple."
I can't see this being the success that the iPod was. It's too big, it's got a crap battery, and it doesn't do anything special. If Apple made an actual e-book reader, that would have been interesting. If Apple made a thinking screen, that'd be cool. But they made a really big-ass iPhone, and stripped it of its phone-ness.
You're supposed to make them smaller and faster, for Christ's sake. Bigger and more periody is pretty much the opposite of cool.