I had my K1 Visa appointment on April 28th. I went prepared. Organization turned out to be key as they officers conducting the interview were very impressed with "my precision" as they put it. I wore a suit and tie and stood out amongst a group of people wearing mostly jeans and a t-shirt. I took the appointment and interview very seriously and it couldn't have gone better. The consular officers were very friendly and professional. Given how ready I was, it was easy for them to get the answers to the questions they wanted as well as the documentation so they started asking non-interview related questions for fun.