*Takes swing at hornet's nest*
The 3G iPhone is the best phone out there. I've fooled with a few other smartphones and see no reason to buy any of them. Between the ease of use and the superb apps, I use it five or six hours a day and haven't had any problems. I had the first gen, too, which was passed along to my father who also loves it.
The only reason I'd tell you to hold off is because there's a third gen iPhone coming in June. Possibly two new iPhones. From what I've gathered at the rumor sites, it sounds like there might be a pro version with a bigger screen, more memory, more RAM, faster proc, and a few other goodies.
If you buy a 3G now, you'll only get the hardware discount if you sign for two years of service. Problem is, you might have to pay full price if you go to the new iPhone in June or July.
Since you could end up paying a lot more, I'd recommend sticking with whatever phone you have now for another two months. It's not that long and you'll probably end up kicking yourself if you buy now.
Also, disregard the fanboys for the other phones.
The new iPhone with 3.0 software should jump ahead of the competition. Comparisons made now will be moot in about eight weeks.