I don't see it flopping at all. There is a large group of people who will buy it just because Apple produced it. I can also see someone buying it if they didn't already have and IPhone or Kindle or MacBook....
It would take quite a run of mediocre products for Apple to lose its allure to a large enough group of its fans and have a product flop. Even being a person who does not particularly care for Apple products I still know that Apple has made quality products that are very useful for a large group of people. They've created quite a following that most companies can only dream of.
Most Apple products fit nicely into a niche that they can dominate. I just don't see the IPad dominating an area where Kindle has such a strong head start or even the netbook niche where you can get a netbook for much, much less. Even though those netbooks may not have the computing power the IPad may, you can still multitask on them which is currently something the IPad lacks. Another thing that would turn me away is not having Flash compatability. Its just the small things that the "hardcore" Apple fans don't see that someone like me is turned off by.
Don't get me wrong, if I could get my hands on and IPad to play around with I would love to. You'd be hard pressed to find someone who wouldn't. It just suprises me that Apple would put out a product that is so underwhelming IMO.