So, I got my 3G in October, where I signed up for a new 2-line AT&T account. Now that the 3GS is out, I want it, but on the iPhone line I would have to pay the full $600 price to get a new iPhone. I checked how much it would be to upgrade the other line, and it's only $400. So, should I pay $400 for the 3GS? Is it worth it?