Yes, I've received one credit so far (and I believe one more pending confirmation), and the MyTesla page updates with the counter. I don't know what happens after 3 referrals, if it will indicate that there are no more available.
What happens to a buyer who uses someone's referral link who is maxed out? I suspect they still get the $1200 credit, but the referrer gets maxed out at 3. It would suck of the buyer gets a message "referrer link bad, please try another".
Yep, we need a way for people to remove their links once they max out.