We paired the Samsung WEP850 with the Apple iPhone 3G. The pairing process was smooth; the phone automatically recognized the headset without us entering the PIN (this might depend on your phone, however). Call quality was quite good overall. On our end, we did hear a bit of static and hiss at times, but we still heard our callers just fine. Volume was quite good as well.
On their end, callers said our voice came through loud and clear. The voice quality was a little on the harsh and tinny side, but it wasn't too bad. The headset also did a good job with its dual-microphone noise-canceling--call quality in a moving vehicle and in a quiet office environment were about the same, for example. There was a bit of background noise when we were in a busy restaurant, but nothing distracting. It didn't do too well in windy situations, though: we could hardly hear each other when we tested the headset in front of a fan. Still, in everyday situations, the WEP850 works fine.
The Samsung WEP850 has a rated battery life of 8 hours talk time and 10.4 days standby time.