The easy answer can be read between the lines of fluckeye's comment: Sangria makes my wife happy, which makes my life easier. In other words, nuclear_fisher, your girlfriend is right. All joking aside, the question got me thinking. Personally, I leave the skin on, although I don't have a good reason why other than it's easier. After a bit of research, including an informal poll among the bartenders at my old college haunts in Lincoln, Neb., (Most of who said, "Man up and drink a beer."), leaving the skin on seems to be the consensus.