I use a dimmer switch and have for years with no problem. You can control the temperature of the UTH with a dimmer switch and I've tested this for weeks. I shoot the UTH with my IR temp gun and it's always within a degree of each other. Some people may argue it's not as good as a thermostat but each have their own set of problems. What if the probe for the thermostat falls or in my case my snakes burrow and what if it gets knocked loose. I can put it on the outside of the tank and do it that way but I find that a dimmer switch works better. I've tried different thermostats over the years and I've always had better luck with a dimmer switch, yes they're meant for lights and fans but an UTH doesn't use a lot of wattage.

Everybody has their own opinion and some have better luck with others, I just like to give people more options versus thermostat's.