I'll forever regret not seeing the Vote for Change Finale show in 2004 at the (then) MCI Center. Instead I went to the Pearl Jam show in Reading, PA a week earlier and decided not to skip grad school class two weeks in a row.
R.E.M. only played 5 songs (The One I Love, Begin the Begin, Leaving New York, Losing My Religion, and Man on the Moon), but it would've been worth it. Plus, the almighty Pearl Jam played "Bushleaguer" at the show, and I've still never seen it.
Great band. I'm gonna spin Monster today in their honor.