Fast forward to today and they've lost that vibe. I'm kinda feeling like the iPad will also lose that after people get used to the 'newness' of the form factor.
In fact, laptops probably became stressful to people just because having a laptop meant you could work--and were expected to work--whether you were at the park, on a flight, on the train, or wherever. An iPad is explicitly unsuited for serious business, therefore it won't be expected to use it for serious business.
Now, I often use my laptop _as_ my desktop computer; hook it up to a larger monitor, mouse, an external keyboard, stereo/video/telescope/interociter/history eraser button/etc. But that doesn't mean that my laptop experience isn't casual when I plop down on the couch, sans accoutrements, and surf hacker news, listen to music, or watch a movie.
And the iPad is more casual still. And the fact that I _can't_ do many things that are not casual may help to keep it casual. Maybe not...
(And for the record, just carry the iPad into the "little room down the hall" for the _ultimate_ in casual computing...)