Why would I need two phones ?
You got a wife or kids on your plan? If so, being able to get a second phone at no extra cost is quite nice.
Of course AT&T won't let you use the second phone for an upgrade, only for a new line. If you are willing to get a new phone number (and are paid up on your current phone) you can just get a new line on your account and then go home and cancel the old second line.
Stupid to make a person jump through such silly hoops. You would think they would want to keep you locked in for another 30 months regardless if it were an upgrade or new service.