Being a server is a tough job and you can never assume to know the many circumstances that lead up to "bad service". After having waited tables during my college years, it has always been my opinion that there should be some sort of manditory requirement that
everyone should have to wait tables for at least a few months! It would be a kinder, gentler dining world....

I still occasionally have restaurant nightmares even after all these years....it is a very stressful job! I agree that only in the case of overt rudeness should you speak to the manager and for crying out loud, let them have the free tip.