Fran and Sharon,
I haven't done much with the big balls but I've heard that they really are good for getting in shape. I'm hoping that maybe over the summer or in the fall I'll be able to take some classes. Sharon, its great that your husband has taught some classes with these. You should be able to get lots of help.
The elliptical is really easier on the joints. I love to run but as I'm getting older, I don't run as much as I used to. I know I can really injure my knees - between running and the ice skating and skiing I used to do... I use the elliptical when I'm not running. I use it on a really high level.
I do alot with aerobics but not enough with weight training. I'm hoping I'll get more motivated for the weight training. I know I sound nuts, but I actually like to run. It not only helps me physically, but gives me a sense of well-being. I love running outside. I do some of my best thinking when I let my mind wander while running... WFEN