I've been opting for the pat-down every time and it does take a lot of time, but in my case for other reasons. Three times now I've opted for the pat down in New Orleans and the issue is there is generally no one around who will do it. So I stand there and wait. Wait some more, and wait more while the TSA agents there stand around talking about their weekends, etc. There's only half a dozen female agents standing around, but they are all 'too busy' to take care of it. Last month when I went through I stood there for 20 minutes. I'm always early, so it's never a crunch for time for me, but I was told 3 times that if I was tired of waiting I could just go through the scanner, that it could be 'awhile' before anyone could pat me down and I could miss my flight. The man in line waiting for a pat down behind me said he wasn't comfortable with the scanners and he would wait, but his flight left in 20 minutes to which the female agent said, in a very rude tone, that there is no radiation and it's ridiculous for people to think there is and it was our responsibility to be on time for our flight, not hers. I looked at her and said it was her responsibility to ensure everyone was properly screened and it was our right to refuse the scanner. When there was a line up of 4 of us, they finally started getting us taken care of when a supervisor came over wanting to know why there were all these people lined up and getting in the way.
I haven't had to do this in any other airports as of yet, but it seems that it's a real issue of TSA pushing their own agenda, and mostly sheer laziness, when it comes to opting out at MSY. I'm not going to be flying through there anymore this year after tomorrow, thank goodness.