Wired has a nice side-by-side comparison of the current crop of smartphones. They feature the iPhone, the Pre, the G1, and the Blackberry Storm. I'm a Pre user, but I've used iPhones in the past, as well as G1's, but never a Storm. I'm getting more and more used to webOS on the Pre, and the slide-out keyboard is worth its weight in gold (I cannot stand the iPhone's touchscreen keyboard, it's the main reason I waited for the Pre). I have lots of friends who swear by their iPhones, and another friend who loves his G1. Some things just come down to taste! The lack of apps, so far, on the Pre is a major downer.
One great thing to think about is the level of technology available on phones now. I've felt for years that phones would someday usurp the desktop, or even the netbooks we have now, and these phones definitely up the ante as far as capabilities are concerned.