I posted already that the iPad will end up being cool because of the apps that aren’t out yet, mainly taking advantage of its larger-than-iPhone size.
Omni group is planning 5 apps for the iPad: OmniGraffle, OmniOutliner, OmniPlan, OmniFocus, and OmniGraphSketcher.
I use one of those on a daily basis, one on a frequent basis, and one occasionally. This is already beyond the iPhone, and it’s because of the screen size. You wouldn’t want to use most of those on such a small screen. (There is an iPhone app for OmniFocus, thankfully.)