I am curious about one thing: how do servers feel about customers who stiff on tips because of bad service?
I worked in an upscale restaurant in Atlanta for 2 weeks before I was offered my current job. In those 2 weeks I learned how important tipping was but also how important service was. Since then my spread on tipping has increased.
I'm willing to tip more than before for good service and i'm willing to tip less for poor service. Consider it natural selection. If you aren't good, then you shouldn't get paid well. That way you will either need to find a different job or get better at the one you do.