One other place that gave appalling service but subsequently made amends.
A pub a couple of miles from where I lived at the time. Nice riverside location, it looked like a nice place to eat. So we went in, found a table (they were quite busy), sat down and waited. And waited, and waited, and waited some more. After about 20 minutes we left, and I sent the pub a somewhat snarky email about how pleased I was that my experiments on a secret invisibility potion were finally beginning to work.
I got a very apologetic email back offering us lunch on the house if we would give them another chance. So we did, we enjoyed lunch on the house (and they threw in dessert, which wasn't part of the original promise), and it was very good. It became one of our favorite places to go, until we moved out of the area.