I bought these a few weeks ago to use when I go running. Overall, I'm not really happy with them.
About 80% of the time I don't have issues with them staying in place during hour + runs. However, every now and then one earbud will fall out repeatedly if it gets really sweaty.
The sound quality is my biggest complaint. My 6-year-old Motorola behind the neck sport headphones finally died. I decided to try a different setup with these Plantronics BackBeat GO2 headphones and I thought I'd be smart by saving $20 or $30 compared to a new set of Motorolas. Well, my old set still blows these brand new Plantronics out of the water when it comes to bass and loudness. I have to turn up the Plantronics all the way in order to (barely) hear the music and the bass is seriously lacking. It doesn't matter which set of ear buds I use. Clarity is very good, though. I have noticed that if any sweat gets near the ear buds or in my ear, the sound immediately gets tinny and distorted. This doesn't go away until everything is completely dry; which is hard to accomplish during a workout.
I'm not a big fan of how the earbuds sit in my ears. I feel like I really have to shove them super far in my ear. I'd prefer if they could just sit slightly in my ear, but they will fall out and I won't hear a single thing if I seat them in this manner. I hated the Motorolas at first, too. So, hopefully, I will get used to the Plantronics. I also don't like how the cord brushes against my neck. I've tried tucking it in my ponytail, but this has the potential to cause issues with the earbuds staying in my ears.
Bottomline: Avoid these headphones and spend less money on a cheaper set of headphones that probably have the same sound quality or just pony up another $30 and go for the Motorola HD S11 headphones to get something with waaaay better quality and fewer earbud problems.