I'm tempted, for the wife.
I started with a pair of "Asian Knockoff" S9's from eBay. Worked ok and sounded fine, until it got even a little sweat on it. Then it would still play, but none of the buttons would work, including the power button - I'd have to turn off bluetooth on my iPhone, at which point the "S9" would time out after a few minutes and power down. Once it dried out, it would be fine again. I eventually broke the band.
I now use a pair of LG Tones, which I'm very happy with. They are a little unusual in that you wear the thing around your neck, and there is a very short cord connecting each earbud to the main device. The upside is the earbud, where most of the sweat will be, is far from the control unit, which stays relatively dry. I've been using it since before Christmas 3+ times a week working out and it's going strong.