Personally, I think they are a mosquito magnet. Put one in your yard and all it does is bring them in from your neighbors. Along the way to the device, they make pitstops at your arm, leg, etc. I put them in the category of Japanese beetle traps. My dad used to put them up around the yard and get a ton of them. When he quit doing it, because it didn't make a difference, he got less, since they were hitting the people around him that did have them.
Just my . 02 on it.