When flamethrowers are outlawed only outlaws will have flamethrowers!
Seriously, though...these things do have a utility for fire crews that need to set backfires in forests and in brushy areas. The way they do this now requires the firefighters to be right on top of where they set the backfire and sometimes the crews get burned.
With the serious versions of these devices they can start the backfires from a safer distance.
I can also see these being useful to people who are defending their homes or businesses from rioters and the benefit is that these devices would truly be a deterrent in such situations. Who the hell wants to get burned?
I think I'd rather see people using a deterrent like this instead of seeing the flamethrower banned and people using legal firearms to lethally accomplish what may have been accomplished without any injury at all.
And, no, I will not be buying one.