Say what you want about Joel but sometimes the guy can knock one out of the park and his latest article on customer service is such a beast.
I've personally worked as a developer for a company that had pretty much the same policies as Joel discusses, and in that time I don't think I ever once had to work with a pissed off customer. I actually had a ton of customers who were amazed that they received such good customer service, and I know for a fact it resulted in more then a few sales. Part of the magic I think is making your customer feel like you and your company are treating their issue like it's the most important issue in the world. Even if at the end of the day you can't come up with a perfect solution they'll still remember the effort you put in.
Another nice bonus that Joel doesn't mention is the simple fact that in our industry nobody stays still. People are moving constantly from company to company and if they have a positive view of your company it's alot more likely they'll recommend you to their new employeers.