I got a call for interview last week and it went off well. The officer asked for a few documents and then congratulated us and asked us to wait outside. After 1/2 hour she came out and gave us the stamped passport.
By the way, a week before another friend got approval notice and went there. He and his wife went at 9:00 clock and the line was really long - they went inside but left after 2:00 pm, as they did not call them yet. They went back the next day at 6:30 am and got it by 8 AM.
All the best...