Unfortunately, I had all kinds of trouble with the 5D. I'd never tried using it in dim lighting before, and no matter how much I fiddled with the settings - aperture, ISO, etc. - the photos had significant motion blur, even with image stabilization on. I tried using flash, but hated the way it washed out the stage lighting. I couldn't understand why I got so much sharper, albeit grainier, results with my point-and-shoot than with this high-end camera.
Finally, all that I'd read and only partially absorbed about photography reached critical mass and I realized the problem wasn't (entirely) my fault; it was the lens. The maximum aperture was 4.0, which simply would not let enough light in under dark club conditions. I confirmed when back home and looking at my photos from Monday night; many were taken at F3.2 (I think I used Program mode for most shots so the camera chose this aperture). These were mostly ISO 800 as well; my shots that did come out from last night were mostly ISO 1600 (except the ones with flash) and still showed blur.
So this was a valuable lesson, not only in finally understanding what people meant by a "slow lens" but also realizing that when I do buy an SLR (which I now hope to do sooner rather than later), I will certainly buy a better lens rather than what comes with the "kit", even though that will significantly add to the expense. (I should add that the lens we got with the office 5D is not a cheap kit lens, it just happened to not be fast enough for the kind of situation I was in at a dark nightclub. We didn't buy it for that kind of shoot, after all.) Right now I have my heart set on the new Canon 40D and EF-S 17-55 f/2.8 lens, but I'll have to try it out in a store first as even the body alone will be heavier than I'm used to, compared to my Panasonic which is not a shirt-pocket camera either. I'm taking a lot of advice from Philip Greenspun's articles on photo.net as he's very smart and takes great photos (but also has a lot more money than most of us).
P.S. to my photographer friends - zahraa, zyxwvut, joedecker, lrc, etc. - please feel free to tell me if I'm completely off-base in either my revelations or purchasing plans. :-)
The other validation occurred upon exiting the club, frustrated with my inability to get good photos and upset that I didn't get a chance to say goodbye to a teacher I'd been chatting with there. A woman at the door recognized me from performing earlier in the week. She said that she really enjoyed my singing. In fact, she said I was probably the best vocalist she'd heard there all week. I thanked her very much and asked if she, too, was in one of the student bands. She said, "No, I'm the manager here." I was stunned... I thanked her again - and walked home very happy...