Thought for the day; if you are nice to people who provide a service to you, they'll provide a better service.
At work I'm usually juggling a couple of projects at once. The clients that get priority are usually the ones that are nice. Which of these clients is going to get something done quicker?
<Client A> You promised this three weeks ago! Nothing's working! I'm going to complain about 10 things that you have no control over. Make the error message bold.
-or-
<Client B> How are you doing? Sorry to bother you, but if you could just make the error message bold I would really appreciate it. Thanks.
The reverse holds true as well. If you're nice to your clients they will (generally) appreciate it and in return give you repeat business. Repeat customers are good.