One of the most useful functions a smartphone can have is the ability to tether. Anywhere you get cell reception you also get Internet service on your phone that you can hookup to your laptop, provided your plan (and phone) supports it. It's been a downer to some that the iPhone 3G was not among the devices to support such a useful feature, but that may be changing.
Apparently, statements from Steve Jobs himself have indicated that Apple and AT&T are working to bring tethering to the unit. This seems to be in response to numerous customer requests to offer such a service. Jobs has indicated that the delays from AT&T and Apple in providing tethering weren't in the best interests of iPhone users, but offered nothing in the way of saying why it has taken them so long to consider it either.