The K1 interview went great. Documents were taken at the first window instantly and 20 minutes later I got my main interview. Just a few brief questions then they said I was approved, I was dizzy, excited and almost fainted. I'm a pretty anxious person but it really wasn't as bad as I had worked it up to being in my head. The 1pm Wednesday slot was a good idea, seemed not to have many people there (3 people ahead of me in line and no one else waiting)
It's still not really sunk in yet! I'd talked myself into worrying about every little detail but it turns out there was no need. "I'm going to approve your visa, it will arrive in the next 14 days" is probably the second best thing I've heard in my life; the first being when my lovely fiancee said yes to marrying me!