iPhone 3.0: Tethering Hero

Daring Fireball's John Gruber posted the following last night:

A decade ago, my first PowerBook was a secondary machine to the desktop anchored at my desk. Now, my main machine is my MacBook Pro, but it feels a bit like an anchor now. My mobile secondary computer is my iPhone

A couple of friends of mine who work in IT administration have been telling me the same thing since the iPhone 3G launched. One of them recently left his laptop behind and took only an iPhone with him on a motorcycle trip and conference, and was still able to keep on top of his servers.

While the sheer volume of writing and editing demanded by TiPb still keeps me chained to a laptop, I'll also admit to leaving the MacBook behind and running out with only my iPhone whenever I can -- and yes, I've been likewise amazed at not only how much I can now accomplish with a mobile computing device, but how easily I can accomplish it.

Have you been using your iPhone as a laptop replacement? How does it fit your work needs, and what have your results been so far?