It certainly simplifies things to say x will replace y. I suspect that with the ipad, its more of the beginnings of a new facet of computing.

For me, as a developer, the ipad certainly won't be much more than a diversion or a target for development. For people like my wife, though, I think it will definitely have an impact. Many people simply want a content consumption device (web, media, etc), and I think the ipad is a very good device for consuming most content.