To stick to topic while trying it out: I got a month of Jazzercise classes from a silent auction back in May and realized I'd better use it soon if I was going to (it expires at the end of the year), so the last two weeks have been a flurry of me trying to get as much use out of it as possible (9 classes so far). It's a pretty good workout--if you make it that way. You get out whatever you put in. Some ladies clearly aren't putting very much into it, but, hey, maybe that's all they've got. Or they just want to socialize. Whatever. I guess I shouldn't talk, since I often have to take the easier options because of my joint issues...
They tend to use pretty recent pop music for the most part and have a cardio section and a strength building section each night (or afternoon, I guess, but I can't go to those). I don't think I'll end up sticking with it after my month is up, since I already have a YMCA membership and don't need another expense, but, if you haven't tried it, it's pretty good. And, I can use some of the moves I learn in the classes in my own routines later on.