My good experiences...
D'Addario strings- when they changed the standard lenght around 1993 or so, I bought a set of strings for my (pre EB) StingRay and they didn't fit. John D'Addario called me on the phone after they got my letter (before e-mail) and arranged to send me a set of the extra long ones. I also got another T-shirt, etc.
Dan Lakin et. al. - So many times. I got my Deluxe 4-94 used, and the previous owner had disconnected the PU coil selector. They sent me a real schematic, a pictorial wiring diagram, and one of the guys at the shop called me to make sure I got it connected correctly. Later I took the bass to them for some minor fret work, and to have the wiring tidied up after I swapped out the Duncans for the Barts (it all worked fine and the wiring was OK, but the stock wiring was SO clean- my eyes were too bad to do a great solder job). Dan met me, introduced me to Carl and then said I could play anything on the wall through any of the stuff they had. Carl spent a few hours on my bass- not only cleaning up the guts, but taking ALL the hardware off, buffing the metal and the wood finsih, dressing the frets, putting on a new nut, and restringing it. Carl brought it to me, watched me play if for a bit, then took it back to tweak the set up. Now, I'd done my own set-ups for 25 years at that time, but Carl NAILED exactly how I set it up myself. Dan apologized that they were out of shirts and hats, and wouldn't take any money- said it was warranty work.
John