My appointment was at 9am however I decided to arrive very early just to be on the safe side. So I reached the embassy at 7.15am. There was already quite a lot of people (30ish) in line and at about 7.30 the staff separated the queue into those who had an appointment at 8am (who were given priority) and everyone else.
After going through security (the button next to the door is a light switch NOT (as I believed when I pressed it) the button to unlock the door), I was issued a ticket by the reception desk. I then waited about 5 minutes before my number was called. The very lovely man at the window took my documents, asked me a couple of questions (such as when I was flying to the US) and told me to take a seat.
15 minutes later I was called up again - this time to speak with an American woman who told me this was the interview. For some reason I felt a bit nervous and when she asked me when my fiance had last visited my mind went blank and I completely forgot the month! However I babbled on for ages about our relationship and after a few minutes she told me she was recommending me for approval!
I was out of the embassy by 9.01am (one minute after my appointment was scheduled for)! So the whole process took less than 2 hours.
I felt like everything was extremely organised and friendly and it would be perfect if the visa itself was issued at the interview rather than having to wait for it.