I really think the dealer horror stories are overblown on internet forums.
I don't. Over the years dealer service and repair shops have left grease smeared on my steering wheel, tools left lying on the floorboard (which I kept), a screwdriver dropped into the shift linkage (front wheel drive car) where it wedged making shifting into reverse impossible, oil and grease smudges on floor mats/carpet, speaker blown by techs listening to music while working, radiator cap left lying on top of the radiator after servicing cooling system, gouge in seat due to tools in tech's back pocket, fasteners not replaced, wrong fasteners used, scratches and gouges in paint, damage caused by making repairs necessitating more repairs, replaced a starter that didn't need to be replaced to begin with (they did reinstall the old starter and refund our money and gave us an apology), keys locked in car, and more.
Once upon a time I was thinking of trading in my 1999 Dodge Ram Pickup for a new Chevy P/U. Technician at the Chevy dealership who was giving my Ram the once-over to help determine it's trade value, backed into a wall. They had to replace the rear bumper at their cost. While I waited.
Another time I went with my mom to pick up her El Dorado at a Cadillac dealer after having it serviced. As we drove into the parking lot, we saw two technicians eating their lunch, on top of her car! They had gone to McDonalds and had everything spread out on the roof of the cab, drinks, burgers, napkins--like a picnic table. Needless to say she went ballistic.
Not to mention the time I ran up to a fool kid screaming around the parking lot in my Honda Accord like it he was in a gymkhana race. Told him to get the f*** out of my car NOW!
I'm sure some people exaggerate or over-react to some things that happen to them, but the stuff does happen more frequently than we like to see.
Of course, I've good experiences at dealerships as well. One recent one comes to mind. I bought a remote control key fob over the internet for my daughter's Kia. Took the car into local dealer to have fob programmed. After about 45 min, service writer tells me they can't program the fob because it's the wrong one for the car. No charge. I really appreciated that.