I got to go to the one here in Champaign for free, when a friend had his friend skip out on him. It was an excellent concert despite not being a huge fan of either of the bands - Weezer did a lot of their favorites, plus a cover of Song 2 that came out of nowhere, and a Foo Fighters song. The frontman was apparently more animated than he's ever been, although I still found his stage presence somewhat...lacking. :p
On the Foo Fighters front, they played a lot of good rock, with a couple breaks in which whats-his-name insulted himself and the band, belched a lot, and bitched out the security guards when they threw someone out for starting a fight down on the floor (like 10 feet from me in fact).
Well worth the money even if you are paying for it, I'd say. Too bad you missed the tickets.
[Edit]: Actually, both frontmen decided to take a walk around the front row, although the Foo Fighters guy jumped up on a ledge without people instead after someone reached out and ruffled his hair.