Growing up with a mom who (still!) is a server, I've been fortunate she's a great one. If she were not a good though... my family would be screwed. Sure, my dad (a chef!) makes a decent amount of money, but my mom's tips account for most of our income. I'm glad she can make so much, but I hate that just a few rude tables or a slow week could completely screw her and my family over. It has it's benefits, but for all the servers out there, it certainly isn't it worth it.
And, as someone who had the privilege of eating at 5-star restaurants (while suffering through the 2nd worst girlfriend in the world) I've experienced positively stellar service. I've left $40 tips where I truly felt my server had earned every penny. But those occasions are rare. Service is a skill. If you get good at it you earn more money. What bugs me deeply is that that skill has to be evaluated on a minute-by-minute basis by inexpert people who have insight into only a small fraction of that person's work experience instead of, say, the manager who can watch turnover, can watch interpersonal skills, can evaluate which wait staff benefits her restaurant the most. Stewardesses don't work for tips. Why should servers?