I actually had a very easy time in Columbus. I went to the offices at 7:30 am on Tuesday 13th April and was directed to stand outside in the rain until 7:45. At 7:45 I went in and joined the surge to the elevators.
Once in the offices, I was checked by a security officer (who was very helpful), gave my receipts, completed I-765, and took a seat. I was called in about an hour later to be finger printed and photographed, and I went back to the waiting room. I left by 9:20am with my card.
It seems they do the cards in groups of 6 people at a time, and one officer worked on these while the rest did the other interviews etc for non EAD related appointments.
I was not interviewed and questioned.They gave me my full year card instead of an interim one.
My Advise: Arrive early!