The battery life on this unit is great. I can use it daily for an hour or so every day, on a single AAA for at least two weeks. (It appears from other reviews that this can vary a lot.)I use this headset with both a Treo 650 phone, and a Apple PowerBook G4. On the Apple, I can use it as a generic output device. (I'm sure the same goes for other headsets.) The signal is strong enough on the Apple to use it from about 30 feet away; on the Treo 650, the signal is not nearly as good.The sound is OK. It's not the best. If it's noisy -- e.g., like driving, or in a hotel room with the air conditioner fan blowing full-blast -- OR if the person on the other end is not talking very loudly, then it's sometimes hard to hear.It'll drop audio -- i.e., the call goes back to my cell phone -- when the battery is getting low. You can milk it a while longer, but that's really your first clue about the battery.The earpiece is OK; it's not as secure as I'd hope. If you're outside in a gust, you may want to hang on to it.Also, people on the other end sometimes can tell I'm on a headset with this one -- they mention that I sound a little staticky.This is my first bluetooth headset, so perhaps my rating is higher just because it's a nifty gadget. But the battery life on this is really the winner -- my work-mates have rechargeable headsets, and it seems like they're always having to charge them. I use rechargeable NiMH AAA's, and they just last a really long time with this unit.