I'm a geek and I run a website written for and by geeks. As a result, I care about the iPhone. To some, my love for a thin phone with a nice screen could be construed as a odd, asocial obsession whereas to others it is considered as obvious as belief in a heliocentric universe or the nitrogen cycle.
Here is a quick checklist for folks who might not be quite as into technology as I am and, as a result, could care less about Steve Jobs' latest creation.
Financial Types - It's probably already to late, but buy APPL.
Bookish Types - You are now writing for a mobile audience. Sure, people have told you that for years and all of your work thus far has some sort of "into perpetuity in all media" clause built into the contract. Well, this is the "all media" they're talking about. People will be able to read your writing on a device about as big as a slice of toast on a screen that looks amazing. If you write for any outlet with a web presence, you will be read on the train.
Drama Types - You're going to be on the iPhone, whether through the magic of IP broadcasting or through the magic of piracy. Sure, if you do the whole "live" drama thing, only excerpts of your performance will appear on YouTube which, in turn, will appear on the iPhone. But be sure you figure out how to do make-up for the small screen. You thought HD video was unflattering... wait until you're squashed onto this thing.
Teacherly Types - Be prepared to confiscate these things. Try one out. You might like it.
Musician Types - You know the drill: Buy new iPod. Rinse. Repeat. The iPhone is probably the best iPod you'll own for a while, so there's your upgrade path.
Folks Who Are Happy With Their Old Cellphone - Listen: your old cellphone is cool and all, but just watch. When someone younger than you shows you an iPhone, you'll be amazed at how long cellphone companies have been putting out ridiculously difficult and underpowered cellphones. The iPhone will define phones for the next few years. You might as well accept that and watch as your old flip-phone begins to look like a Conair $5 drug store landline phone.