I've had 2 mustangs and they both made pretty great horses. The first one, I bought from the original adopter as a completely unhandled 3 year old stud (they adopted him before they realized that wild mustangs are actually wild LOL).
My Dad helped me put the first couple of days of training on him and I've done all his training since. He's one of the very best horses I've ever owned and I wouldn't trade Dobe for anything.
He's a heck of a cowhorse for not having a natural cow-savvy bone in his body
And he's got a heart the size of Texas. You put a rope on something and he'll either pull it or break tack trying.
The other that I got was 4 when I bought him from his adopter. She'd already sent him to one trainer who sent him back as "untrainable". So, when I got him, he wasn't even halter broke. Due to time constraints, I had to turn him out for a year and finally got around to pulling him in and getting him started when he was 5. He made a nice enough horse but I never clicked with him the way I did with Dobe, so, I re-homed Koda a while back. His new owner loves him to death and spoils him rotten (in a good way LOL).
This was one of his first rides at my house
And this is him with his new owner
Other than some serious spooking issues I had to work through, they were both relatively easy to break. Neither ever offered to buck.