Although we found the sound to be loud it could have been also much clearer. The big issue was the echo that both parties can hear. The M2500 also has a tendency to pick up outside and wind noise but not too much to make it annoying. Plantronics states that this headset has 5 hours talktime with 120 hours of standby with a non-replaceable battery. From personal use, finding that it was actually half that talk time. It takes roughly 2 hours to charge fully, and for the travelers, unfortunately, the M2500 does not come with a car charger.
Along the lines of buttons, the M2500 is like other Plantronics headsets. The power button is a tiny, clickable, rocker switch above the LED. The rocker is used as the power, mute and volume control button. This a bad design because getting use to the device we had a few accidental mute calls instead of turning up or down the volume. There is also another small button around the end of the microphone used to answer, hang up, redial and voice dial. But at different occasions we found that it is inconsistent with use, not always hanging up.
In all, the Plantronics M2500 is not the best headset out there but its low price makes it very appealing. For constant work use, it might be best to look around for a different headset, perhaps paying the few extra dollars for better quality. Occasional and value-conscious users would find the M2500 to be a very nice option with a low retail price of $89.95.