My Interview Experience, Chicago, DO:
Did mine in Chicago on Feb. 22nd. First I was asked swear under oath that you're telling the truth and nothing but the truth, and then came a quick firestorm of questions about things in my application. The whole thing was mostly painless. Because I'm a college student who goes to school out of state, they asked me to show them my state ID or driver's licence, and I gave them my licence from my home state with an explanation of my situation, and showed them my proof of enrollment and current class schedule from my school. It seemed to count as sufficient proof of residence in-state for them.
Then came the test of reading, writing, and civics: they were a piece of cake, and the interviewer stopped after the sixth question for the civics part since I answered everything correctly.
Being an asylee derivate before I obtained PR status, I was rather worried about showing them my passport since it's long expired and I haven't used it at all since coming to the U.S., and as a result I don't have it on hand. I used my Re-entry permit as a passport for the one overseas trip I made (not COP), and just to be on the safe side I also brought with me photocopies of my expired national passport in case they ask for it. It turned out my worries were for nothing, however; they were satisfied with my re-entry permit and didn't even mention my national passport. I was asked about my overseas trip and I told them the destination and that it was under 90 days.
I'm getting a name change, so they verified that at the end, and I was asked to sign a bunch of documents, some with my current legal name and some with my new name. I was then given a sheet of paper that said I passed my interview, and asked to stay in the waiting area until they call out my name and give me my oath letter (not sure if this is the standard practice for other DOs, but this is how they do things in Chicago as of last month). After over an hour of waiting, I had my oath letter, hot off the press, in hand. One thing I noticed that most people's oath date were within the week, so I assumed that unless you request a name change, you should be able to take your oath within the week, perhaps even within a couple of days, after you pass the interview. There weren't anyone who got to take their oath on the same day that I know of, but I'm not entirely sure if it was because there weren't any oath ceremonies scheduled that particular day or if it just wasn't the practice in Chicago DO.