Took a couple of tries to get a good molding (the included directions are a bit overdone and end up making it harder to fit properly).
They stay in place, and I noticed no difficulty breathing compared to the Reebok guard I had been using. Talking isn't perfect, but speech is intelligible. Screaming "man on" is no problem.
My bite isn't "correct" so finding the right guard has been difficult. These worked well, though, because of the generous supply of gel, but with no plastic frame like the Shock Doctor guards.
Whether it's better than a $2 guard though, I don't know. Personal preference I suppose.