I know this thread is defunct, but just wanted to say that I bought an Arab/Saddlbred cross this year (he's registered as a Half-Arab) and he has a fantastic temperament. He's not hot at all, but pretty easy-going and tries to please. If something startles him he'll spook, but not a dangerous spook; he just jumps a little.
When I was looking for a horse, the last thing I wanted was a hot, crazy horse, and when I saw him for sale, I almost didn't go see him because of the reputation of the ASH. But his owner insisted he was calm, and she was right. I don't know if they're all like this--maybe not, from what some have said here--but I'm very blessed to have found him.
He's a beautiful mover and has great potential as a dressage horse. That's him in the picture on the left.