I have got one. Its very good for tidy ups but if the weed roots are well established it doesn’t kill them. For safety I always hose over the area I am going to use it on. The aim is to “cook” the weeds, not burn them so the water actually helps.
Where I need to eradicate tough weeds, I use high strength glyphosate in a spray. I choose a dry still day and shut the dogs in for an hour or we go out for a drive. I then WAIT, maybe for the whole season. I think that the reason most people find that glyphosate doesn’t work is that they either clear the tops of the weeds away once they look wilted, or they don’t see anything happening so they re treat the weeds and this burns off the top growth, Either way the roots are protected and re shoot. If you just wait, then the weedkiller travels to the root and kills that too. I have managed to kill ivy and entrenched stinging nettles by using the apply and wait strategy.