The kill shelter I adopted Buddy from kept him for 3 weeks after finding him after he had been dumped off in the woods, even though he was so deathly terrified of everything and everyone that he wouldn't even look anyone in the eye. All he would do was cower in the corner of his room. He was so terrified that they couldn't put him in a cage near the other dogs because he was so afraid of the other dogs when they would bark!!
They turned a small office into his own little room. There was one man at the shelter that Buddy grew to trust. He was the only person Buddy would let leash him, or pet him.
I think that qualifies as a good kill shelter.