I was at the transmission shop shortly after they opened this morning. (I had an early-morning conference call that I had to attend first.) The owner said the problem I reported sounded easy to fix. This afternoon, he called and said I could come pick it up. I walked over and he handed me the keys. When I asked how much I owed him, he said, "Nothing." There was a loose cable preventing the shifter from moving, it was an easy fix, and while it was technically not a warranty repair, I've done enough business with them that he wasn't going to charge me for it.
Edit, 23:30: Since good customer service deserves a plug, note for the record that the shop was Fremont Aamco on Thornton Avenue.