I have a Ranco for almost a year now and no problems. Works great. Even wired it my self.
It does a great job for the money. But in the RBI rack I switch to, I get different temp readings in different tubs. And even though They are constant, some are 3-4 degrees off each other sometimes. Just annoying for my self really.
Also Im living in a studio now and it makes a ticking noise everytime it turns on and off. It's very loud when the Ranco is brand new. It will take a while for the noise to come down.
I would like to upgrade to a herpstat to give differential t-stats a try, and to have a back up thermostat in case one breaks or anything else like BallsUnlimited said.