I'm a little curious as to why it's only being offered at Cingular/AT&T.. if you could unlock it, T-Mobile operates on the same frequencies. I think they may have coated Apple's pockets a little to make it available only with them.. but the question is, just how much? I mean.. Cingular has been way behind the curb when it comes to multimedia offerings the like that Sprint and Verizon offer. Hell, only recently did they get a decent selection of phones.
Honestly.. I wouldn't pay $600 for it. My reason? It's with Cingular. Horrible CS, holes in the coverage area, skimp on warranties (I know, I know.. there's no such thing as a "good" carrier). I'm still stuck in contract with them, but I may buy it out. I've had 3 different providers so far.. and while they don't have the coverage map of other networks, I have to say T-Mobile has the best customer service.
Basically.. I wouldn't want to be caught in a 2 year contract and a broken IPhone. Cingular/AT&T/Bellsouth megacorp isn't going to use any lube when they ream you up the rear, and nickel & dime you for everything (charger, plan, etc). Those of us in the south who are familiar with those in charge of the new merged company knew it previously as Rapesouth for a reason.
A true CAG way of doing things would be signing with Cingular for a year, taking the free crap phone they throw at you.. purchase an unlocked phone of your choice & switch the SIM, then take the money that's left over and get a standalone MP3 player that you don't need to pay Itunes to purchase the songs for it