My Wife and I went for the combo interview here in Atlanta and It was a breeze. The IO did not care about the delay in filing of I751 at all. He just asked a few standard questions like when were married, where we lived, How many children and where we both worked" Cleared that in a few minutes. Asked about all the items in my Wife's N400, Civics, English questions and passed us and scheduled us for the same day ceremony. Our Appointment was at 9.
We were there by 8.15 and were done by 12.45 and out of that office.