Here is may experience from the interview.
I arrived to the USCIS office at 8 AM and my interview was scheduled for 9:05. They called my name at 8:10.
The lady who had my file askedfor copy of my GC, but I told her it is stapled inside my passport because my I-751 is pending. Then she said "Shi*****" and appologized for it

She asked if my husband was with me and I said no, since during the infopass they told me that he does not need to come with me. Then she told me to wait and transferred my file to the other gentelman.
The IO was very nice. He said that they are seeing more and more cases like mine, where I-751 and N-400 are both sent to them for approval together. He said he already had 3 cases like this last week. Since my husband was not with me he said some IO sent people home and ask them to come back together, but he said he never does that (nice ha). He reviewed my I-751 paperwork, asked if I have any new papers and I gave him new phone, gas, electrical and my 401K bills showing our names.
After that, he asked me 6 citizenship questions ( very easy), I wrote and read one sentence and he said that my case was approved. Gave me a letter saying that both N-400 and I-751 were approved.
I was there around 25 minutes total.
Sounds like you had a reasonable logical thinking IO, good for you. It's not like you get your green card out of a Cracker Jack box, even though I feel that is where some driver's got their license from. We had to provide a stack of documentation about 1 and 1/2" thick, copied on both sides as proof to get that first green card, both in English translations and the originals in Spanish that costs us a huge fortune, but I wonder why the USCIS has a Spanish speaking line? I spend way too much time wondering, LOL.
Do you live in Chicago or in the suburbs? How did you get there? Both the Milwaukee and Chicago offices are located downtown with one big fat, no parking sign. The St. Paul office is not located in St. Paul, but in Bloomington right off the interstate with lots of free parking. My wife's friend lives only sixty miles north of St. Louis, but in Illinois, so they send her to Chicago, she has to take the train and spend about 200 bucks for the cheapest hotel room. She gets called into Chicago with her I-751 with no reason only to be told they lost her proof, she had to go back again with the proof, that wasn't reasonable.
We have to go down there for my wife's consulate, debated whether or not I wanted to spend five bucks for a cup of coffee, did, but wish I didn't, tasted like it was made from the water of the Chicago River. Ha, tell my wife when we go there, we have to bend over, because we are going to get it in the rear. Was born in Chicago, but with the spirit of my ancestors, got out of there when I was able. That whole downtown is making money with money, can't eat money, don't they believe in work?
Does anybody know how long you have to wait for the oath letter in Chicago?
Thank you all for support and good luck!!!!!!
Danutuke