I always opt-out and I never have any problems. However, when I opted in DEN few days ago, I got a very sarcastic and irritated TSO. Even though it is not a back-scatter radiation, I still don't want to be exposed to extra health risks. The TSO that told the male agent that I wanted to opt out, rolled her eyes and pointed at me. Then I told them I wanted to keep my eye on my stuff, so the agent sarcastically picked it up and said I can't touch it. During the pat-down, he asked me if I do this often and I said every time I have to walk through a scanner I ask to opt-out. He said, if you do this all the time, I should know that the scanner at DEN is safe and does not utilize radiation. I said I know, but still would prefer not to go through it. It wasn't that bad of an experience, but left a bad taste in my mouth.