I ride my horse bitless only. Sometimes in a rope halter or just a cordeo (trails included), but if we're doing serious training, then a simple sidepull with a soft leather noseband it is. I have no reason to use a bit on him (though I trained him to accept it, just in case he someday needs the skill). He responds very well to bitless training and has been going bitless since he was first backed.
As for the benefits - I used to work at a lesson and trail riding barn with many horses who had problems with novices hanging to their mouths. Some of them started becoming sour, balking, nervous and showed other unwanted behavior. One by one the horses were then switched to rope halters and bitless bridles. Since then all the horses started regaining their calmness and eagerness to work again, so the benefits were just huge! Also, bitless bridles are very comfortable in trail rides (the horse can drink and eat easily) and they benefit to horses who have trouble accepting bit because of health reasons.
I have come a long way, to surrender my shadow to the shadow of my horse.