I have not had any real bad experiences, but I sure have heard of the usual ones... oil change places that take out the oil, replace the filter, and send you home about 4 quarts low.... valve jobs that let you go home with no valve cover.... etc...
My sister once took her Nissan to Sears for tires. She called me to come and help because something was wrong with the car. She got the tires and tried to leave, but the car was hard to control. When I got to the lot, I checked the lug nuts first. Sure enough, most of them were missing and the ones that were there were not even close to being tight.
I brought the service manager out to the car, he apologised, tightened the nuts, pulled the car back in the shop. After about 30 min. the car was pulled back out and the service manager refunded her the entire cost of the tires. They also replaced all the mounting studs because the rims destroyed most of them.
It was just a simple mistake, the tech was just not paying enough attention or there was a mis-communication between the two working on the car. We begged him not to refund the tire cost, because there was no major harm caused, and they fixed the mistake and damage.... He insisted we take the tires for free... I guess the cost came out of a couple of tech's pay!
I still go there for my Michelin's and reccomend that shop to all my friends and family.... We get a royal treatment.... wonder why!?!
76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles