Sure, the iPhone is a sweet phone (even at $600), but how does it compare to the less definable internet tablet category?
All four devices have feature-complete browsers and can take advantage of the rich web 2.0 applications their larger cousins can. And each offers some local applications, including media players. But these aren’t general purpose PCs, and they’re not trying to replace PCs. These are information age devices that deliver the network in places we generally don’t bring our laptops.
The iPhone is the smallest and lightest of the bunch, though it also has the smallest screen (counting both pixels and inches). Still, it’s claimed battery life bests everything but the famously power-efficient OLPC. Yet even the 8GB iPhone isn’t the most expensive of the bunch, and the 4GB model is just a bit more than the least expensive publicly available tablet.
Mix the mainstreaming of social software over the past couple years with a device like this and step back. Twitter was just the start. Still, the iPhone might also find use among ebook users (though what we really need is a browser-based book reader) and for other purposes.