Many of them were very sensitive and tended toward over-reaction, especially during the training phase. If you ever got one broke enough you could trust him, then you'd have a stellar horse...but getting them to that point wasn't for the faint of heart.
the mare I mentioned above I ADORE, to the point I'm selling my 3 year old I really like and buying her instead. She is hardworking, athletic, honest, intelligent and responsive. Exactly what I want in a saddle horse for myself personally. Near as I can figure(all conjecture) She was owned by someone and kept at a barn with an indoor, blanketed and in her own pasture. I'm guessing she badly intimidated her owner with her sensitivity and reactiveness, so she was sold. She can turn right out from under you if you don't pay attention. But an awesome, awesome little horse, with tons of heart.
two of the doc bar horses I worked with were sensitive to the point of being explosive, they could out buck most rodeo horses, and they were in general a huge handful. Athletic? Yes, extremely. Responsive to cues? To a fault. Recreational rider friendly? NOPE.