If you've been having an issue where you can't log into Battlelog because you still "have to buy BF3", but you have it on a console, fear not! If you have an EA account, just link your gamertag to it, then play a round and score some points. That'll get you on.
If, however, you can't do that -- for whatever reason, perhaps the 'add new persona' button is gone, as it was for me -- get into contact with an EA rep via http://help.ea.com/, and ask them to link your accounts. Be warned that this may set your Veteran status back, however.
Just putting it out there for anybody still having trouble :)