A couple of points:
It's disturbing how many cannot see the potential of the iPad as an e-reader to kill all e-readers. I'm a musician and a technology consultant, storing resource kits, song books, and the like is going to be extremely useful.
Anything more than that is just a bonus here...and it's a last resort remote desktop/VNC device when I'm in a bind. I can browse the Internet without having to boot up a machine. Can my phone do all of this? Yes. Not quite as useable though. This isn't a giant smartphone, that's what you see at first glance. Anything I need a sheet of paper or book for is pretty much made obsolete by any device the size of the iPad.
Tablet PC/Slate? I already have a laptop, the simplicity and LACK of configurability and multiple hardware platforms actually are more enticing to me than the opposite. My laptop is a company/government owned machine that I do not use for entertainment...why would I want to lug around a second laptop or for that matter, buy one?
I'm no Apple fanboy, the only Apple product I've ever owned is an iPhone - yes, I even refused to purchase an iPod for years...and I'm not "excited" about the iPad, it's just a must-buy item for me, a tool that I plan to use. I'm sure there are many others out there like me, the people buying this thing aren't just giving in to marketing or spin from Apple.
If you consider the iPhone a fad, unusable, or a product of marketing, then there's no hope for you. Continue to be the vocal minority on the Internet who prays that every next gen phone will be an iPhone killer. Good luck with that.