I've taken some decent pictures at a concert with my Canon SD300, without flash. The key is to use the menu and select "Night Mode". It helps a lot, but shutter speed is still an issue (without jacking up the ISO). Also keep in mind these guys are jumping around, so blurry pics will be common. Using the continuous shooting mode will help. Wish I thought of it before I screwed up 80% of my pictures.
You can also consider taking video clips. At my last concert (SoaD), I took 688mb of video with my SD300 (320x240@30fps, about 20min). Turned out pretty good, but sound was, of course, crappy at best.
The best part was "Security." They frisked everyone before we went it, felt right over my camera in my right pocket, and wallet in left, and asked me if my phone was in my thigh pocket (it was). They even missed my friend's pocket knife clipped to his right pocket.