My husband had his interview 7/10/2015. From what he told me, it was a fairly painless process. His appointment was at 1:00pm and he arrived early as to not be late. He was able to get through security easily and they even let him take his messenger bag in.
He went inside and waited in a large hall with about 100 other people. He was first called up to hand over his paperwork, which he had all organized making the process easier. After that he had to wait about an hour to be called up for his interview. The lady behind the counter was nice and asked him three questions.
1) How did we meet?
This lead into the long story of how my husband and I have known each other for 10 years and were friends before we started dating which she commented on how nice that was.
2) Where was he moving to in the US?
3) Who Douglas was?
This is my stepfather and joint sponsor.
That was it. He was approved and free to leave the embassy. A rather painless process if you have all your paperwork together. Though it is rather anticlimactic.