Everyone has different experiences. I've dealt with several seriously reactive, nervous, bucky Doc Bar offspring, but heard other people love them.
I typically avoid halter and western pleasure breeding like the plague, but my 4 year old is halter on the top, pleasure on the bottom, and the most willing, cooperative mare you can ask for, and very intelligent, she thinks through every scenario. Too smart actually, she steals the BO's fencing tools and dumps them in the waterer just because she's bored
I have seen people that can't stand thoroughbreds, but I have worked with a lot of good ones. Every horse is an individual.