I have reached out with my issues directly to Fitbit, but they believe the product works.
I have several Fitbit devices, and have for a few years now. With this one beware if your steps matter, because they will randomly wipe out for the entire day. And it has happened repeatedly. I have multiple devices active, but never in use at the same time. Per Fitbit the only reason for the steps to disappear is that one is more accurate, so apparently they believe it's the one not moving.
I very highly recommend Alta, but definitely do NOT recommend the Flex 2. I was drawn by it being waterproof, but I'm farther ahead to not get credit for any water activities than to keep losing hard earned steps.

Okay, so I didn't think I would love this as much as I do. I'm not a very "fit" person - I don't go to the gym as a hobby, I don't count calories, I don't drink protein shakes, etc. - so I thought I wouldn't get very much use out of it. However! I use this thing all the time, and it even motivates me to keep moving! I love that you can set your own goals, too. I run three times a week, and it recognizes that as my goal. It's interesting how it keeps track of your sleep, too.

The battery charge doesn't last for very long, but I think it charges fairly quickly. I usually just charge it when I'm sitting down to watch TV or something when I won't lose any tracked steps.

If you're on the fence about this, I would say go for it! It's the cheapest one and it isn't super bulky. It's very discrete, so it doesn't look so out of place when you have to be dressy, which is something I don't like about the Apple watch or some of the more intense Fitbits.

*UPDATE* so like three days after posting this review, my dog ended up chewing my Fitbit while it was charging. I contacted their customer service and explained the situation and told them I've had it for less than two weeks, and despite dog chews not covered under the 1-year warranty, they replaced my tracker for free. I'm actually amazed by their customer service. I contacted them late Saturday night, and by Tuesday morning my new replacement tracker is preparing to ship. Just wanted to share how insanely helpful the Fitbit customer service is.

First, this is my 4th fitbit product and I have LOVED all of them... except for this Flex 2. I really wanted and was excited to switch to a waterproof fitbit for summer time. But it is soooo not accurate. At all. It typically records less than half of my steps. It sometimes syncs and I lose half of the steps it did record. I have done all of the app updates, reset the fitbit, etc. This isn't my first rodeo with a Fitbit acting up. All of the usual tricks did not change the fact it still isn't accurate. Super Bummed.

Upgraded to this from a Fitbit Charge. I loved the charge but after a year, the battery wouldn't hold a charge and the band literally fell apart. This wasn't the fault of the Fitbit; I work in a cafe so I'm constantly washing either dishes or my hands. Even being careful it got wet a lot, and I suppose even water resistance has its limits.

The difference between water resistant and water proof is why I went with the Flex 2, as opposed to just getting another charge So far it's held up beautifully, I do try to remember to take it off at the end of my shifts and wipe it down, just to be sure.
As for actual functionality, I'd say it compares well to my charge. I like the minimalism of the display, and the clasp on this band is MUCH better than on the charge, which popped off my wrist more than once.
I especially like the various alerts, including the reminder to get up and move. It's motivated me to take laps around my kitchen island to get my steps a couple times. No shame! And as someone who regularly gets up before 5am, the silent alarm is wonderful. It wakes me up easily without waking my husband. That's a huge bonus in my book.

Overall, this seems to be fairly accurate in terms of step count, although I'm not as dogmatic about that as some people. I just want to know that I am moving throughout the day, and that I have some accountability to myself when it comes to reaching my goals. The only thing I wish is that I could set the auto-detect for active minutes a little lower. My walk to work takes about 7 minutes, and if I forget to turn on exercise tracking, it doesn't always get counted. That's honestly my only gripe and it's a small one.

This is a great tracker, it works well, charges quickly, and once it's on my wrist I forget it's there. It's been a great help in striving for my fitness goals.

I have never had a fitbit or anything like it, but my friend came to me, one day all excited about her new fitbit, so I decided to get one, that very day. My fitbit flex 2 arrived last night. The fitbit flex comes with 2 decent plastic bands, a small and a large. I chose the small, to wear, which is a pretty good size. I downloaded the app on my I phone 5. I charged the battery and I attempted to sync the fitbit to my phone. The fitbit did not sync immediately, but as soon as I turned my blue tooth off and on, the fitbit synced rather quickly to my phone. I put the fitbit on my wrist. It is quite comfortable, but a little sweaty, once you really start moving. I am an overweight person, and I have not exercised in quite some time. I have to say, I was extremely motivated today, I was excited and determined to go from 0 to 10,000 steps. I was over the moon, when I reached my goal. The fitbit dashboard on my phone, is amazing, it tells you your steps, food intake, calories burned, water intake, sleep activity etc. I am anxious to see my sleep recordings in the morning, over all I am happy with my new toy. Hopefully this will give me the push, I need in 2017 to make some better lifestyle changes.
UPDATE-January 13, 2017-My advice, give yourself a realistic goal, don't get me wrong, 10,000 steps is achievable, but it is really hard to do, if you are focused and motivated, you can do it. I use music and I do some stepping in the morning, at night, of course throughout the day. FYI- I love the sleep tracking, it is pretty accurate, it tells you how many times, you wake up, at night, how many times, you are restless, when you went to sleep, when you wake up, I am truly addicted to fitbit.
UPDATE-February 25, 2017-I am still doing at least 10,000 steps or more every day. I love the challenges within the fitbit community. There are friend requests and you or other people can challenge each other, to see who can do the most steps, in a day, a weekend, a week. I really love goal day, where each person strives to complete his or her goal. The challenges are really a great motivator for me, to continue to exercise. The challenges, drive me to do more steps.
UPDATE-APRIL 28, 2017-No problems with my fitbit, still love my fitbit, still using it and still getting 10, 000 steps or more in a day:) no longer a couch potato
UPDATE-JUNE 30.2017-No problems with my fitbit, still love it, I have started to use the food log, which is on the dashboard of the app. The food log is great, you key in what you ate and it automatically pulls up the food and you add it to your log. It is good because it allows me to be more aware of all the food, I have eaten. It also tells me, when I have gone over the amount of food, I am allowed to eat for that, day, according to my weight. I have lost 20 pounds, still loving my fitbit:)
UPDATE:SEPTEMBER 11, 2017-Fitbit still works great, no problems. I am still addicted to hitting my steps.
UPDATE:NOVEMBER 18, 2017-Fitbit still works great, problem, fitbit didn't reset itself one day, at, midnight, but there is a small button to reset it on the back of the charger. I am doing 20, 000 steps a day and still loving my fitbit. I actually got it wet, for the first time in the shower, I was too afraid before, but it still works fine. I really love it. This is my last post, hope it has been helpful to you.