I had not logged into my battle.net account in 6 years. In that time I had swapped phones thus loosing my authenticator and the email I had used was hacked by a spammer and deemed locked forever by Microsoft. In less than 24 hours support was able to utilize other forms of my ID and got me back up an running in time to try the Diablo II Beta weekend. So impressed.
Years ago they had also helped me recover my items in WoW after a person got into my account. I have always been impressed with their responsiveness and ability to calm a worried gamer.