Actually, I've used my coffee can chimney stoves and their smaller sibling places where open fire was banned and becuase the embers are contained it is kosher. I also brought along a cut down #10 to act as a base, so there was minimal scorching of the ground.

Of course, I've also had a thumbs down on them. It depends on your location, and I always get such authorizations in writing. Odd how different people read the same regs differently.

The biggest advantage I see with this kind of thing over a fire is time. Needs less fuel, so you spend time gathering, it gets hot quicker, so you spend less time cooking, and it goes out quicker, so you spend less time twiddling your thumbs before you can be moving. Time is one of the few things you can't put in a pack.