My husband's interview was in February in Port-au-prince, Haiti. He received a phone call on a Monday morning, and was asked to come on Thursday morning. He needed to bring, more wedding photos, proof of our communication, and all stamped pages from MY passport showing I had visited him....which I had, 5 times since our wedding last April. I put everything together and flew down 2 days later to attend with him. I brought a list of potential questions, and we practiced a bit the night before going to the embassy. On the Thursday morning, we attended the interview at the embassy. My husband was interviewed by a French Canadian woman, and had a Creole interpreter present. He was in the room at least 30-40 minutes and I stayed in the waiting area. He then called me in and the officer asked if she could talk to me and I had no problem with that. She asked me most of the same questions she had already asked him. At the end she was satisfied the marriage was genuine, but there was a couple more things he needed to provide before she would grant the visa. (DNA test for the oldest daughter, and the consent form from the mother of his youngest daughter).
Just to add, I know it is not required for the sponsor to attend, and it's not always possible. In our case it made a BIG difference. My husband answered all the officers questions, and he gave very thorough responses...i could hear him talking through the door! But, she still told him she was not satisfied the marriage was genunine. She was very surprised to hear I was at the embassy also, and had flown down in such short notice. Getting to speak to me made a huge difference I believe.