My interview was scheduled quite late in the day so when I went to the consulate there was no lines and I could go in straight away. I was about 15 minutes early because I had read there's not point in being much earlier. In hindsight I'm sure that I could have been maybe 30 minutes early and they would have let me in too so if you are scheduled at a time that's not that busy try to go earlier.
Security was like a simple airport security. They told me not to turn on bluetooth but nobody checked my phone. I had read before that immigrant visa are issues in the second room but all interviews were held in the first (again, maybe because it was at the end of the day and not many people were left). I went to the first window and the guy said the person at the second window would check my documents and he would call me so to take a seat. I did, and I waited for a while but nobody called me so I finally got up to check and they had forgotten about me! He even said he already turned off the computer! The guy was apologetic about the situation and thanked me for coming up and waiting so it was not a big deal. He explained there were 2 parts and that he just needed my documents. He took everything except the proof of relationship. They take all 10 of your fingerprints. While he was waiting for his computer he asked me some things but this was small talk. Then I had to sit down and wait for the second part.
The people were called to the second window in the order we came in. There were 2 people in front of me and we were the only people still there. Like other people said, there's not much privacy and I could hear both the consulate officer and the person being interviewed very clearly. I did not mind as it gave me a sense of the tone and questions asked in the interview. Everyone in front of me got approved. When it was my turn there was nobody left in the consulate so I didn't have to worry about privacy. Like everyone else I had to raise my right hand and swear I was telling the truth. Then they took the fingerprint of my left 4 fingers again. He looked through my documents and asked me a couple questions. They are not difficult if you have a genuine relationship. Questions asked:
I had a whole folder of relationship proof but he only asked me if I had some pictures of us together. He looked at maybe half the pictures then gave them back to me! He said thank you for answering all my questions, I'm going to approve your visa. And that was that!
There was also a person there (not for a visa) that seemed to be intoxicated and the security staff was very helpful and kind to me and came to check on my twice.