Many of the horses in my area are ridden in American TTs. I rode my first gelding in an ATT, mainly because that's what the previous owner rode him in and what he was used to. I never had any evasion problems with him in that bit, and I eventually switched to English riding and an eggbutt snaffle. I rode Scout in the old ATT bit one time (I'd been riding him for a month or so in the eggbutt, the switch was sheer whim on my part), and he HATED it. Head tossing, no brakes, minimal steering snorting, half dragging me back to the arena gate. I put the eggbutt, back in his mouth and he was a gem. I may one day choose to put some better neckrein knowledge in his head and take him in some western events, but I plan on getting a bit like the one posted earlier, with the Billy Allen mouth.
Bits don't make horses good or bad. Riders do. Horses have preferences. Some (my first horse, and may others that I know) can handle bits like the ATT without complaint. Some (like Scout) hate the things. Big whoop. Some horses hate french links, too. I'm certainly no diehard supporter of the ATT, but there are far better made, better designed, and more useful bits out there. If I borrow a horse who is fitted with the ATT, I don't throw a fit and demand a snaffle bridle, I'll ride with the same discretion I use riding any other bit with a shank. Scout threw a totally out of character tantrum with the ATT that vanished with the snaffle, ergo I am not surprised, and will likely purchase a different curb if I choose to switch back to western for any reason.
A stubborn horse walks behind you, an impatient one in front of you, but a noble companion walks beside you ~ Unknown