yeah, I too am on the fence. My mare is pretty lazy on the overall and does not have a tendency to take off when spooked, more just scoot around. So when trying it she was easy to control when she spooked, however she is only 3 and still green and I fail to see how if something came up I could use an emergency stop on her, yes I could pull her in a circle, but sometimes that is just not enough.
I've seen some great things out of them from other riders, and in fact saw a big jump in training progress from a friend of mine using the bitless for only a few sessions. The mare was nervous and is a higher strung horse -the bit was too much for her with leg aids and so she tried a bitless and although she reverted back to a bit because the control wasnt there on the motor, it got her mare past the point of confusion and nervousness to start working the bit on her.
There are good and bad things for sure, it is a unique concept, but definitely has to be for the right kind of horse.