If you've been using them for 20 years, I wouldn't exactly give 'em hell. Assuming the management is still the same, they should still be a trustworthy shop. Maybe send them a letter explaining that you have always trusted and enjoyed their service, and that you understand they are going through some growing pains, but you feel like your recent experience wasn't up to par. Let them know about the 2 mechanical problems and what you feel was an overcharge for labor. (not to mention if the mechanic missed the control arm, you probably don't have too much confidence that the bushings were done properly) Don't threaten or even ask for anything- just let them know how you feel about their service.

If they are worth keeping a relationship with, they should come back with a reasonable response.