My initial experience was in person at ORD and mostly consisted of a tutorial on how to use the machine. There was the moment where the person reviewed my list of countries visited, looked me in the eye and said "you didn't include Canada" I almost said "I don't really think of them as a foreign country" but stopped myself and just said "I must have forgotten that one" - my list was long.
The first renewal I lucked out. I think the whole first batch was renewing at the same time and they opened a second temporary office in the customs building in downtown Chicago. It was odd since the building doesn't get a lot of visitors and they didn't quite know what to do with me, but they got me up to the office, which was one sort of bored agent who looked me up hit a button and said "you're renewed". 2 minutes, max.
My second renewal was online with no problems.
Now, though, whenever I go through most of the machines are broken (EWR, I'm talking about you!) But when it works it is brilliant. If I land at ORD international terminal with a good gate and a good seat on the plane, and with no checked bags, I can be at the curb looking for my driver in maybe 5 minutes total.