Want to make a sales person crazy? Ask them to wait while you read the fine print. Or better yet - ask them to read it for you. Especially if you suspect the contract contains a "Loyal Customer Penalty" (TM):
"Requires new two-year AT&T wireless service contract, sold separately to qualified customers; credit check required; must be 18 or older. For non-qualified customers, including existing AT&T customers who want to upgrade from another phone or replace an iPhone 3G, the price with a new two-year agreement is $499 (8GB), $599 (16GB), or $699 (32GB)."
I'm sticking with T-Mobile. And these guys.
Walls are meant to keep people in or out (and once in a while both). So I guess a lot depends on which side you happen to find yourself. :)