I have an unlocked/unbranded S2
I looked at the S3 the other day at an AT&T store. A couple of odd things i noticed was:
The 4.8" screen didn't look any bigger than my S2 with a 4.3" screen. When I held the phones side by side, the S3 has a much longer screen, but it really didn't seem any wider.
They really made the S3 thin. It looks beautiful without a case, but if you dropped it without a heavy duty Otterbox case, it would be over.
Burst Shot is a neat camera feature.
It has NFC, but i don't know if i would trust NFC. My wifes new Nokia 808 has NFC.