Melanie,
This is the first time I've visited these boards (awesome!). I was doing the FIRM tapes regularly (4-5 times a week) from Jan - May of this year. Then summer hit and I haven't worked out since. I plan to start again tomorrow (our kids went back to school on 8/6).
I noticed very nice improvements in my arms & legs and behind. My husband even noticed very soon after I'd started working out. One word of caution, tho. You do use weights and my program came with a large step (fanny lifter - and it really works). Shortly after increasing my weights on these fanny lift exercises, I noticed problems with my knees and had to drop down on my weights. I started with 2 lb weights, then went to 5 lb, then 8 lb and I found that my knees just could not handle the 8 lb weights. I went back to using no weights when doing the fanny lifter.
Since I am just starting again (after my summer hiatus), I plan to use weights for my arm exercises, but will not use any weights at first for the fanny lifter. In addition, I have bought knee supports to wear.
All in all, I love The Firm and think it did a wonderful job in sculpting my body. The think the thing I liked most about it was the combination of aerobics and weight training. Unfortunately, I must have weak knees. Just be aware.
Good Luck!
Lissa