I think you hit the nail on the head with the cooking example. I think there are many uses like that, that will give the iPad a broad appeal.
As a matter of fact, I can think of a few such uses myself. Despite my gripes about how the App Store works, I’d love an iPad myself. It’s a matter of weighing the drawbacks (closed ecosystem) against the benefits. Unlike the iPhone, I think the iPad is pretty unique right now.