There have been issues of a rash developing from the Force, almost like a burn, which is not easily treated. I've seen the story posted on Facebook, and while I don't always give credence to these kinds of reports, the fact that it's happened to people I know in real life gives me pause (only one degree of separation makes it more real).
It appears that this issue affects users of all colors and all sizes, and is most likely allergic in nature given accounts that people are using stronger steroid creams (such as triamcinolone and fluocinolone) for treatment. While there are some very rare reports of this occurring with the Fitbit Flex (also worn around the wrist), the overwhelming majority of instances are with the Fitbit Force, which suggests the culprit could be the altimeter port or charging port, both of which are not on the Fitbit Flex. The delayed timing of the occurrence of these rashes suggest a contact dermatitis or delayed hypersensitivity reaction, with many users not developing symptoms for over 2 months. Fitbit has been faithfully honoring their policy of refunding or exchanging any culprit devices
However, I love the sleep tracking feature, and the alarm. When that thing starts to vibrate, you get up. It doesn't let you tap it and keep snoozing! It only stops when it registers you moving enough to be getting out of bed. And when you reach your goal, it lights up like the 4th of July. Sometimes that startles me, when it starts vibrating wildly, but it's nice. It's like your own personal cheerleader.
The interface on both the app and the online site are great. Very easy to use, to read, and to add to it. I find that tracking my water intake as I go, through the day, is much easier now. I just quickly enter it into my phone. I haven't developed the habit of using My Fitness Pal to log my food, so I haven't made use of the fact that the two products sync up. Which also means that the FitBit telling me how many calories I've burned can't possibly be accurate.
At any rate, I will continue to use it. Would I buy it again? I'm not sure. I doubt I would bother with a regular pedometer, since I think they all have the same issue: they count steps and it depends on how it is reading your motion, which depends on where and how you wear it. If you're just getting started in fitness and you need the motivation to walk, or the reminder to move more, then I can see the value. Once you're already doing those things, I feel like a heart rate monitor would be more effective. That, or I just expect too much from a device like this. I want it to measure everything. I want it to know my REM sleep, my heart rate, exactly what I've eaten without me logging it manually, how much I weigh ... basically, I want it to be magic.