I've been using my Plantronics 510 since December 4, 2005, and it has performed flawlessly throughout. Incoming audio quality is excellent and I've never had a complaint from anyone concerning sound quality on their end; indeed, most are surprised that I'm using a wireless device. I routinely recharge the unit at conclusion of each business day and, unlike a previous reviewer, I've yet to have a problem. Only tonight, I paired my 510 with an AT&T Bluetooth-capable home cordless phone system, which will allow me use this outstanding product in my home office, as well as when I'm on the road. I spend hours each day on conference calls and I'm looking forward to the comfort afforded by this extraordinarily well-designed device.