Just wondering why you think they'd be controversial... They're only a tool (and a poor substitute for proper leash training) but I haven't ever thought they'd be controversial...
When I managed the humane society here, we had young teen volunteers who would walk some pretty big, burly, untrained dogs and the Haltis and Gentle Leaders worked well to help get the dogs outside for walks and keep the volunteers from getting pulled willy-nilly down the path.
Most of the dogs got acclimated to the feel of the head harness quickly and because they knew it meant a W-A-L-K, they became very willing to accept it.
I've never needed one for my own dogs, because they are taught proper leash manners from an early age, but, "in the right situation" with a very strong puller, it can prevent the pulling (but not necessarily teach the dog why it's not OK to pull...)
It's a prevention, not a cure... IMO...