In my opinion, they barely get the job done. If your room temp fluctuates a lot then you will be stuck changing the dimmer a few times a day. Even with the dimmer, the UTH can still spike at times.

I have used light dimmers and I had problems. I switched to the reptitemp 500r and that was the best thing I could have done. It was so much easier and I never had to change it once I set it. Now I use a johnsons controls because I have a rack system. I have donated my reptitemp to my friend who is a new snake owner Just sharing the love.

Rheostats are a temporary fix.
Thermostats are the only long term solution.