In fact my experience has been opposite with respect to popunders. I previously worked for a decent sized website startup. We had a huge debate in the company on whether or not to try out popup advertising. The sales team wanted it, the products team was totally against it. Finally, as a compromise, we decided to go with popunders. It was a lead generation form for another website. We were amazed at the amount of money we made from them. Definitely shows people are not averse to checking out a site if they are a popunder.
Next up, since popunder advertising was cheap, we tried promoting our own site as a popunder. Not only did we have pretty good sign ups, the user engagement on the landing page was pretty good as well. What we learned from it was that maybe the regular tech-savvy users you could find here on sites like SitePoint hate popups & popunders. But for a regular joe, he is not averse to checking out a site if it is not extremely intrusive and is interesting.