I've got the complete opposite with one of my horses. Barcoo is the ideal riding school horse - he'll go for absolutely anyone, but me. With me he'll buck, bite, bolt, pigroot, rear, refuse to walk on and just be a pig in general. With anyone else he's the perfect angel.
Until anyone takes him to a competition. With my cousin and friends, he's bolted, he's bucked, he's reared, he's done just about everything but roll. I'm the only person who has gotten him to perform. This horse has carried me to so many ribbons and trophies it's not funny. It's kinda weird. He's not to be ridden at home or in lessons by me just because he goes off his nut but as soon as we're performing together (must be in front of a crowd), he's perfect.
Joe will go for both me and his new owner. Me because he knew me and his new owner because she lets him jump instead of having him do dressage all the time. Toby will go for anyone at the moment just because we're still getting to know each other.
I've been told that it's approximately one year before you get really used to your horse, two years before you become a team, three years before you become one. =]