I built a PID controller system for my pot years ago. Since I was designing and building process heating control systems at the time, it made more sense than spending 50 bucks on a thermometer. I had controllers on hand - stuff which had been returned under warranty or something someone burned up the output on in the shop. Dug them out of the trash and used them to walk people from across the globe through setting one up over the phone in the middle of the night. Some minor repairs and they worked. Had all the other stuff handy as well, so, why not?
Since I rarely get a chance to actually focus on something for more than ten minutes at a time, it's been very handy. Started using a hotplate for the same reason. Have to go find a dog? Set the mould on the hot plate and go look. Need to rescue a cat, add softener to the was, see what the commotion is back of the house,... set the mould on the hotplate and go do.
A few years ago, I actually went online and BOUGHT some parts to set up both the pot and my pizza oven for PC. Bought the pizza oven years ago to form Kydex. I've got a few spare controllers left and was thinking about getting a bigger box and making it a dual-controller to control the hotplate too.
Necessary? No, but it was convenient for me and pretty much free, except for rescuing a few controllers and fixing them.
I cast sort of inside - in my garage, which is WELL ventilated, meaning very hot in the summer and very cold in the winter. I cast when ity's just too damned ugly out to do anything else - usually when it's well below freezing, blowing and snowing. I dress for the occasion and point a Big-Buddy propane heater at my butt and cast as long as I can. An hour is good, Two is a gift. I leave everything set up and steal an hour another day and another if I can get away with it.
Last winter, I never got the chance, but the winter before, I was able to get out there several times and made a big pile of bullets. I just cast and cast - whatever mould I haven't cast with lately.
It may be perfectly fine, but I'd personally avoid the pots with the integral PID controllers. You get stuck with the controller the manufacturer chose and if the controller goes bad, the pot is no good. If the pot goes bad, the controller is useless. A separate controller leaves yoiu many more options and is also not as close to the heat. Electronics don't always appreciate heat and those controllers look awfully close to the heat source to me. Like I said, they may be just fine.