How about a bluetooth keyboard on my lap and an iPad propped up on the coffee table in front of me? Of course, for typing urls or short messages it will be the same thing I have to do with my iPod touch now, hold it in one hand and peck with one finger using the other hand.
Sitting with it on your lap and staring down on it to type would lead to a lot of neck pain. I think people are missing something that is being left unsaid by Apple: The iPad is intended as a viewer more than as an input device. Sure, you can type on the thing, but it is better suited for watching movies or reading ebooks (if you don't mind the backlight).