I just had my interview earlier today, and here's my experience:
I arrived 2 hours before my interview, and everything was done in exactly 2.5 hours.
I must say the waiting experience felt a little awkward, being able to hear all the interactions between interviewers and applicants, and with nothing to do other than looking over your documents. That alone adds to the stress, so I think sitting close to the TV and distracting yourself with CNN wouldn't be the worst idea.
For the interview itself: The CO (interviewer) was a friendly, understanding yet no-nonsense kind of person. I was honest and answered the few questions he asked me truthfully (the usual questions; where I met my spouse, last time we saw each other, etc..) and the interview duration must have been 5 minutes or so. He approved my case and wished me good luck.
My take-away after today is: Be well-prepared with documents they may need, stay calm and answer honestly. Overall it was a positive experience and a good day at the end.
Wishing you all the best of luck.