So the registration for early access seems to be working already at the following link:
Go to : http://na.square-enix.com/
Log in to your account
Go into "My Profile"
Go to: "Add new game"
Enter your code from your receipt. There are two different formats.
However, I entered both my codes I was give by EB Games (Gamestop) and when I hit "Check Code" it came up saying it was FFXIV:ARR (PC).
Does anyone know if the Early Access codes are universal to either PC or PS3? I'm on PS3 and so I refrained from fully registering my code as we don't even have a PC capable of playing ARR. Or has someone tried their PS3 code and comes up saying it's PS3 version?