The ball links are used a whole bunch on the GS aerobatic models but with a caveat or two...

You usually only find them on the servo arm, not the control horn and those servo arms are either metal or some other high strength material which can take the torsion being applied to them from the control surface. Never use them on the control surface horns unless you have a model using two horns parallel to each other on each surface and the ball link is in between them.

They are also used a lot for metal control rod throttle linkages on the gasser (two stroke gasoline, not glow) engines which helps to isolate the electrical impulses from the engine's ignition system to the radio equipment. Lots of times you'll find them on both ends of those installations, but they also have a metal or HD servo arm and usually a metal arm on the carb as well.