BILL– My answer is a very qualified “yes,” with is use restricted to particular, extraordinary circumstances relating to reclaiming horses with histories of certain kind of abuse. In such a context almost anything that works—anything that puts the horse more at ease and in a physical or mental frame which makes him more susceptible to accepting the rider’s influence without fear—is OK with me.
Beyond that situation, I don’t generally see a need to use one. The chatrooms and message boards talk up bitless bridles (and bareback dressage, for that matter), and if riders want to go those routes, it’s harmless. But if you’re interested in competing, which means developing your horse to work within the confines of mutually agreed upon rules, then you might as well train that way too.
A good seat and sensitive, empathetic hands will serve you well without the need to use other devices.