My girlfriend and I both purchased MiBands about 2 months ago and have had them for 50 days now. I have Android & she has IOS. I'm running the tweaked app and she is running the stock app. We both have enjoyed the bands thoroughly and constantly compare stats for accuracy.

Accuracy

• Step count - As one should expect from such an inexpensive device the accuracy isn't perfect. Don't expect it to give you an exact step count or even to be 100% consistent with someone else doing the same activity. That being said we've never noticed more than 10% difference between our readings. On average we are usually within 5% of each other after doing the same activity.

• Sleep Tracking - We've found the sleep tracking to be very accurate. It's never been off by more than 20-30 minutes, but I would attribute that to it not knowing the exact moment you fall asleep vs lying still. I've tried laying it on the nightstand before going to bed to try to trick it, but it always knows I'm not wearing it and won't record a sleep cycle for that night.

Water Resistance

• Everyday use - Both of us have showered with the bands on everyday since day 1. I've noticed that small amounts of water will get into the "pocket" the device sits in, but I usually just gently dry it off and slide the bracelet up a little to dry my skin underneath it.

• Outdoors - We recently came back from a week long trip to the Caribbean. While we were there we; snorkeled in the ocean several times for a total of about 5 hours, hiked through the woods in the rain for hours, swam in fresh water streams, and zip lined drenched in sweat... The MiBands are still holding up strong since our return home 3 days ago!

We were both highly impressed that they survived the ocean water (we figured worst case scenario it was a $17 lesson learned). They even tracked our movement in the water which was even more impressive! I dove down about 8-10 feet several times to grab various creatures / items off of the sea floor, in case anyone is wondering how deep I took it.

The bands held up fine against all of the sunscreen, heat and sweat we threw at them as well. I haven't noticed any color changes or deterioration.

My only complaint is that while we were zip lining the device popped out of the bracelet once... Fortunately, one of our guides saw it happen and handed it to me. I don't know how it happened. My only guess is that the ball of my wrist pushed it out since we were sweaty and doing a lot of lifting / twisting movements.

TL;DR

These bands are waterproof and tough as nails in my experience. They have survived hours in the ocean, depths ~10 feet, sweat, sunscreen, brutal heat and humidity, falls around 5 feet onto wooden slats and dives off of rocks into fresh water from about 15 feet up. If you're an active person I see no reason to take it off other than to charge it. The band itself is my only complaint as I wish it held the device more securely.