This is the second pair of these I've bought; I got my first ones in June 2015. I wanted another set after the play/pause button started to stick on my originals.
You might wonder why I'm giving a headset a five-star review if I had to rebuy 'em. It's because these are the first sports headphones I've had that lasted anywhere near that long. I'm rough on equipment. I run in the rain and mud, onroad and off, and I sweat more than it's comfortable to admit in a public forum :) I went through four sets of Sennheiser sport headphones in a year, and prior went through three pairs of Nike sport headphones. I consider myself a special case of rampant hardware abuse when it comes to sports headsets.
These headphones have never left my head working out. Jumping around, running, powerlifting, elliptical trainer, rowing machine, sprinting, burpees, dancing, whatever, they do not come off. They're wireless too, so you don't beat yourself in the face with a cord. I have tried a couple different types of headphones and these are hands down the best for staying attached to my head when I'm behaving like a lunatic.
The sound quality is good, it's not as good as say Plantronics' own noise cancelling headphones, but they're still better than (IMO) something like Beats, or Apple headphones if you're used to those. A point of note though is that the microphone on these sucks, it's worse than a MacDonald's drive-through. I've used a few boomless designs in my time (Sony Wireless Gold cans, Plantronics Backbeat Pro, Bose QuietComfort, etc…) and they all work pretty well. These Fits do not. This is fine for me, because when I'm running I'm gasping and swearing and other things people shouldn't have to hear, but if you're buying these for service as say Skype headphones I wouldn't recommend them.
If you've bought them before like me, you might be surprised to find the arm band / pouch is no longer included in the box. Also, for those like me who don't RTFM, you'll need to use the app to select a voice language, otherwise they just chirp at you without the usual audio prompts.
Battery life is excellent, they're about 8–9 hours for me regardless of how I use them.
I've paired them with a Mac, PC, and iPhone, all work fine.