Samsung Galaxy S3 AT&T $499 off contract...worth it?

1saleaday has the AT&T Samsung Galaxy S3 for $499 with free shipping and no tax. I know most people recommend going with a Galaxy Nexus but does this lower price point (compared to regular off-contract price) tilt the scale in S3's favor?

Also, the site states it an unlocked AT&T variant? Can someone please explain the difference between this and one I would buy directly from AT&T? I thought you had to buy the international version to get an unlocked phone.