Works good, surprised how well it works considering the price point. I got the version with more attachments than most, figuring it would be more versatile.
Works just as advertised, anything metallic inside the coil gets heated up rather quickly. Takes less than 30 seconds to get a 1/2" nut red hot, to break it loose from the bolt. Note I am meaning a nut that fits on a half inch bolt (fits a 3/4 inch wrench). It does this using electricity and magnetism and no open flame.
The coils should work as long as the insulation holds. The insulation seems pretty heat resistant but if you wobble enough that it touches a red hot bolt, it will melt a little and smoke, so protecting it while in use should help them last longer.
Overall it works very well, and at a decent price point. Just a few years ago, a similar tool would have been more than double the price.