Is "The Firm" a good workout? How often and how long did you do it?
And how long did it take for you to finally start seeing results?
There are dozens of FIRM workouts now, so there's lots to choose from. I am only personally familiar the Classic FIRMs that originally came out, and those are EXCELLENT workouts, and were groundbreaking for their time.
I'm not as sure about the newer ones - they are actually made by a different company now, but they seem to be pretty popular. You can find out more about them at the Video Fitness Forum, along with reviews.
As for results - I found myself getting stronger and feeling better within a couple weeks. I don't know if I can really speak to weight loss results because most of the time I was using them, I didn't diet, and the time I lost the most weight, I was obsessively counting calories. the VF forum does have reports from lots of people who felt they got great results.
I have the classic ones too. They are amazing in my opinion.