Yes, I've had one since my birthday in July. I've not worn it in a few weeks because I took it off when we went to the US at the end of October...
So thanks for reminding me to put it back on - lol!
I was going to start wearing it again Sunday, but the battery was very low so I put it on the charger here at the PC & then forgot about it.
I agree it's a good tool (electronic WiFi pedometer) for gentle motivation to move from being more sedentary to being more active, getting in more steps, more flights of stairs, etc. And there's an online forum centred around it - where you can interact with other Fitbit friends for support & competition (I haven't done this).
At first, I was fascinated with the sleep thing, but I stopped using it for that after some time. I didn't find the reports on 'sleep efficiency' particularly meaningful. It seems to register anytime you turn over in bed as a 'time awoken' - which may or may not be the case. And on occasion showed I was awake as much as 20-30+ times in a night, yet still said my 'sleep efficiency' was 90%+. When I tried explaining this to my GP, he in turn asked - well what exactly does all that mean or signify (i.e., sleep efficiency, the number of times you turned over)? And I couldn't really give him an answer...
Also, I just got tired of wearing it at night - having the thing around my wrist.
The other thing I found was it doesn't really accurately capture all my activity at the gym - for instance, all the strength training & weight lifting & stationary bike, etc. It only measures steps (treadmill activity, possibly crosstrainer - but not sure on that one). So Fitbit might register that I've not been especially active (lower count of steps, not meeting the 10,000 daily step goal) when in fact I've been super active via means other than steps. So it does have its limitations - I think I probably need some other kind of tool for better reflecting that activity (I'm sure my trainer would suggest one for me -- just not sure I want to spring for the money on it). Fitbit does sync with My Fitness Pal & several other online apps, such that Fitbit would tell My Fitness Pal about my steps & flights of stairs etc, then I could input my gym activity on My Fitness Pal in addition - giving me (via My Fitness Pal) a truer idea of calories that I burned. I got tired of doing all that extra data input though!
I think it's great for someone who is purely looking to get more steps in. For someone who is routinely more athletic, they might find its limitations disappointing - but that's not the sort of tool that Fitbit is.
PS - I've lost about a stone & reduced my body fat composition since I got the Fitbit -- but I think that's owing as much (or more) to the gym than the Fitbit, although I'm sure they both help. And I'm still a big eater who loves to booze it & eat decadent sweets.