I lost over 2 stone of baby weight when I got mine!
It is the only piece of fitness I've ever stuck too!
The challenges are completely addicting, it's so nice being able to use it along with friends! It's so motivating to get your move on! I have a problem with being competitive and when I first discovered the challenges I did a 2-3 mile walk every morning so I had done my 10 thousand steps straight away before any general walking around! I lost 8lb in the first 3 weeks of having it and then the rest from there!
I also find with walking every part of my body tones up, so even if you are not looking to loose weight it motivates you to stay healthy.
Another interesting feature of the Fitbit is the sleep tracker. It was particularly interesting when having a newborn baby to see how little sleep I was getting!
I've been really pleased with mine and absolutely think they are worth the money:)