I think ot has different effects on each horse and how they respond to things like this. I would,definitely try it for yourself because it has great effects on my horse who had trouble calming and focusing and this him has helped a lot!
I think it's really good! I have GumBits and it really helps keep young, green horses really focus and not be to worried about everything else going on around them, especially at a horse show. For stubborn horses that won't go on the bit, I've heard that it helps relax their jaw from chewing the gum.