Per my fiancee's experience, she arrived about 90 minutes before her scheduled interview at 9 am and the wait ended up being about 3 hours long. She was called to interview, and was asked how she met me, how I proposed to her, and whether I'd met her family. She was then told that the K-1 visa was approved and to expect it in the mail in about 2 weeks. Overall was a peaceful and painless experience.