I won't buy one right away. For one thing, I just spent too many dollars on a netbook, so I won't be able to convince my wife that I NEED one of these for a while, but if it is as good as the ads claim, then it may be a home run for Apple.
I wouldn't be able to use the 3G version (lousy AT&T coverage both at home AND at work) but the WiFi version might be useful. When I travel it is heavy and inconvenient to carry multiple books. A tablet like that would fit in my satchel and provide reading material for an entire trip, not to mention reference material when I go on a mission trip (as long as I expect to have electricity!). It's about the same size as a lot of the books I carry, and much smaller/lighter than many of the references. Somebody else noted that it's a bit too large to handle with just one hand, but I rarely hold on to a real book with just one hand. From what I've read, it sounds like a nearly perfect size and shape for a lot of the reading I do.
There are some disadvantages. I can't imagine that I would do much typing on a touch screen keyboard. It probably can't do much picture editing and there's a lot of applications that require more processing power than they can put into that kind of device. It certainly won't be replacing desktop PCs any time soon. Even if it had the processing power, I'd be reluctant to put Turbo Tax or Quicken on something that could be easily lost or stolen.
Still, there's a lot to be said for a well designed entertainment device that has all the features of the iPad.