Not posting from my iPhone... yet. I'm waiting for my activation confirmation e-mail.
I'd told myself I was going to hold out for the second generation iPhone, at least. See if 3G support was added. See how other people liked the iPhone after a few months use.
But all of the reviews looked so good. And the local Apple Store still had them. And I was there picking up a new Mac Mini for my father, and got to play with a display model.
After that, I couldn't resist.