I've had this headset for about 9 months now and I am very pleased. I have previously owned two different models of the Motorola "MOTOROKR" (S9 and S10) and neither of them fit or sounded nearly as well as this product. I kept the S9 for 2-3 months until it stopped working due to perspiration seeping into the electronics - I returned the S10 for fit and sound issues. I did run with the S9s, despite the fact that they didn't fit well or provide good sound, and the fact that they lasted for nearly 3 months is a testament to their durability, but in the end they still succumbed to perspiration getting into the electronics.
I do a number of things to keep fit and they're all more fun with music - running, cycling and weight training. For cycling and working out at the gym, this headset works flawlessly. The sound is as good as a good set of earbuds. I perspire about as much as any normal, hydrated person, and these activities don't cause the device to stop functioning. Running on hot days or doing cardio workouts at the gym are a completely different matter and I use corded earbuds during those activities. Since the headset's design doesn't fully hug the wearer's head, I wouldn't consider them to be well-suited for wearing while running anyways because they would continually shift or rock in place.
No device made of these materials and costing $50-60 will be completely sweat-proof. Only a small part of the headset comes into contact with my head and I occasionally wipe that part down during long exercise sessions and afterwards I clean the entire unit with isopropyl alcohol to keep them clean and reliable. If you take care of this set, it should last - if you abuse them, expect them to be completely sweat-proof or waterproof, you would likely be better off with a good set of corded earbuds, as they will cost you less money and last longer. On two separate occasions, the controls have stopped responding due to high perspiration. Leaving the unit alone overnight allowed proper usage to resume the next day. Again, proper care will lengthen the product's life.
I have observed the behavior where the green power light comes on and doesn't turn to blue indicating the successful Bluetooth connection. I fixed this in 30 seconds by restarting my iPhone to reset the Bluetooth stack and it instantly connected. I'm a little dismayed that someone with the time and knowhow to create a video documenting this problem couldn't be bothered to consider that the problem might lie elsewhere. Commons sense will make this product, as with anything, more worth the investment.
Pros:
Reasonably comfortable, even when worn together with Sunglasses and/or a bicycle helmet
Sound comparable to earbuds
Multiple earbud sizes to customize your fit
All controls fully compatible with current iPhone/iPods with current firmware
Subdued design and appearance - no obvious flashing lights or logos
Long battery life
Cons:
Not adequately protected against perspiration or water for some activities
Good for:
Cycling
Weight/resistance training
non-exercise related listening
Not good for:
Running/Cardio
People who sweat a LOT
People who expect this product to be something it isn't