I asked this question along time ago myself.
Just my opinion, but......
If you want to get toned, then it's probably a great tool for that. If you have the brochure or the tape, or seen the commercial it's primary focus seems to be on weight loss.
If you want to get bigger, then I think free weights are the answer. I finally passed on it, because although I want to be toned, I also wanted to get bigger. I ended up buying a bench, a smith machine (I work out at home with my wife, but occasionally we have to solo it), and a few other peices of equipment....pretty much a full gym, and it was less than a bowflex.
You may also want to keep in mind that alot of people buy equipment and NEVER use it past the first couple of weeks.
The bowflex looks great, and they certainly know how to sell it, and even offer a payment plan if I recall. However, I would find it hard to believe that the people in the commercial gained mass with it.
In a nutshell, I think free weights are better.