Chuck,
I don't have any experience with horses, but I can tell you that with some breeds (not all) you can expect an occasional challenge to the pecking order. I find this usually occurs some time in the spring or summer, after season is over and when I haven't worked the dogs very often. They get used to living in the house, where I'm not as strict on obedience as I am in the field.
This challenge isn't violent or aggressive. Its usually passive...ignoring a command or two, walking away with something I've told them to bring, delaying on a "sit" or "Here!" command.
The real advantage to the "smarter" breeds is that they NEVER forget what a command means. You shouldn't have to retrain, only reinforce.
As for "natural retrievers"...all of my dogs have been natural retrievers. They would perform adequately in the field, by my standards...they'd probably be considered "fine dogs" by many of the people I've hunted with. But, just as we take pride in the guns we hunt with, I take pride in the performance of my dog. Sure, you could hunt with a JABC, but why would you if you could be hunting with a Parker or Fox?
