I may have purchased this for different reasons than most. I use it for a repeating silent alarm throughout the day (one that is not my cel), tracking heart rate at the gym/hiking, and tracking sleep. I don't really care about steps or calories and those really seem to be what the device is made for (although I haven't checked its accuracy).
Out of the gate, it had a problem starting. It was supposed to automatically sync during setup after it was charged, and it wouldn't. I had to search online to troubleshoot it, and there were many other people that had the same problem and few different things to try it, but the info provided with the product was not helpful.
The display is supposed to come on automatically when you turn your wrist to look at. Doesn't for me. I have it tagged in the setup info to be on my left wrist, which it is. But it will display when I'm moving my arm in every direction except how one would look at their watch. The alternative it to tap it. I know it's not a touch screen, and one shouldn't expect the same responsiveness, but I have to tap it hard 4-6 times to get the display to show. It's especially annoying when the alarm goes off (which I use very frequently) because I have to keep tapping it several times to turn off the alarm otherwise it will go off again in 9 minutes.
The heart rate monitor is pretty consistently 10-20 bpm off when I'm on cardio equipment at the gym that can also read my heart rate. It doesn't matter what brand of cardio equipment, what type of exercise, the Fitbit is always much lower than the reading the equipment gives me. I've tried both tightening the band and sliding it up my arm, but it doesn't seem to help. It seems to be worst when I'm sweating so I don't know if that interferes with it somehow. (Which you can see might be an issue when exercising). I know I can get a reading from the machine I'm using, but I wanted the fitbit to actually track and record my heart rate, which is proving challenging. Plus, I have very little faith in the readings it makes when I can't cross check it with anything else (hiking, running outside, etc).
The sleep monitoring is interesting and useful. I have nothing to compare it to, so until I know better the time I spend in each stage is what it tells me it is. Much like how I planned to use my exercise information, I like that I have a record to see how I'm doing over time.
And be aware if your skin is fairly sensitive to touch, the device itself gives off a strange pulsing feeling while you wear it. It is odd. I don't love it and it's a good excuse to take it off whenever I'm not trying to track something. Be warned.
I would have definitely given it a 2.5 rating if that was an option. I probably would have gone down to a 2-star rating, but I do still use it everyday and plan to continue using it because it's the only option I have for what it does. I just wish it did most things better. I wasn't expecting perfection, but I am disappointed. After you break the seal on the box, I'm not sure it's returnable for any reason other than it being defective (I don't know), but even so I feel you need to spend some time with it to really get a feel for it to decide how it works best for you. Other than the display being a pain in the ass to work I'm not sure any of this technically counts as defective, and even the display is seemingly more a function of poor design than not working the way it is supposed to. It's just not a great product.