What's your opinion on them? Have you ever used one? I was thinking of buying one (specially designed for brewing, even has a tap on). How is it different from the more traditional methods? Is it worth the cost?
I suggest you build your own. There is a great how to build a heat stick thread on homebrew talk.
I have heard that carmelization is not an issue using immersion heater elements.
In order to provide enough heat for a rolling boil you will need 220 VAC and at least a 4000-5000 watt element I believe.
Electricty is dangerous, so is propane. Make sure you take every precaution neccessary. And use a GFCI.
I use a heat stick for raising the steps in my MT, heating strike water, and heating my sparge water.
I use an Ultra Low Watt Density electric heater element in my RIMS to control mash temperature..
No problems so far with carmelization.
What's your opinion on them?
Have you ever used one?
How is it different from the more traditional methods? Should be the same as traditional brewing. Boiling is boiling. I defer to my comments on the element itself above.
Is it worth the cost?
I hope this answers your original questions.
setting a stirring bar in the wort should lower the hottest temperatures developing in the areas near the element by sweeping cooler wort to the coil. This should eliminate carmelization. Additionally it will quicken the heat up time since the coil will transfer heat faster to a cooler localazide wort.