While ebo's and tronics (if they are still around) tend to be the most highly recomended, I have never had a visi-therm fail me and have been using them for about 12 years. I own 16 of them right now, 6 of which are over 8 years old. They are not all currently in service, only 7 are at the time, but they will be as the other tanks get set again this winter. I did explode one when I plugged it in while it was out of the water and then put it in the water (don't even ask how that happened it was a bonehead move) I have had them get hot when they were inadvertantly turned on while out of the water, but as long as I let them cool first they show no side effects when put back in service. If my Visi-therms ever do fail me I'll probably switch to EBO's, but for now I am quite happy using the extra cash for other things.
Dave