720 degree polish... why do it?

Because if you polish your shot 720 degrees (that's two complete turns of the tamper for those of you who are math illiterate) you are more likely to get a nice uniform pack of your portafilter basket. What you are basically doing is coaxing the finely ground coffee particles into more uniform proximity to each other, and therefore getting a better extraction, in most cases. As Steve Goldberg, our Espresso Evangelist, intelligently pointed out at a training session at Cafe Limbo this afternoon, when he started polishing his shots consistently, he started getting more consistently good shots. So polish, all you baristas, polish well!