Had my interview today, the whole thing took about 10 minutes and was very pleasant.

I was honest about the question of illegal drug use. The agent didn't ask what, only when. I said it was 30 years ago. He didn't even break his rhythm, continued with the questions and then showed me how to use the kiosk and sent me on my way with my CBP sticker.

He said I would get a confirmation email in a few days. I'm guessing everything was ok, but I hope my honesty doesn't disqualify me.