^Well said, smrobs!
My guys aren't "using horses," they're basically glorified pets compared to some of the horses out there, although I would like to get Scout very used to working around cattle soon. I let Dad watch half an hour of cutting and now we think about how handy it could be to use the horses to move the cows sometimes.
Anyway, groundwork can only go so far, unless there is some reason to not ride. Yes, it can be a big part of "relationship building," but so can riding, to perhaps a greater extent.
Some NH schools of thought like laying a horse down as a way of really blowing the horse's mind. To me, strapping a saddle to his back and mounting can blow just as big. Psychologically and instinctually, for a prey animal, that has to be a pretty big thing, nicely carrying something on what thousands of years of instinct are screaming is a landing strip for predators. Properly preparing is necessary, but groundwork can only go so far. Sometime you've got to get on. I'm of the general opinion mini's were invented for people who want to do groundwork only.
I agree with smrobs that usability and respect come first. Every using horse I know is a gem to be around. I know several horses who are constantly being messed with (hey, there's a right way and a wrong way to do groundwork, too) on the ground, and are rarely ridden, whose owners want to be friends with their horse above all. Those are some of the least pleasant, least respectful horses I know. I find that when the horse begins to respect the rider (Respect of persistence, consistency, timing, and feel, not of domination or fear) he soon starts to do the "relationship" things; meeting me at the gate, nickering when I walk up to him, bobbing his head when he sees me coming out of the house with the saddle. I've seen people start training the relationship "tricks" that a well bonded horse exhibits, and the horses end up treat-grubbing half ton poodles.