I love this headset!I bought this from Amazon after reading 100+ reviews and comparing between Voyager 510 and 520, as well as other products. Overall, I'm extremely satisfied with the sound quality and how comfortable it sits on my ear.I don't know if the standby time can really last 4 days (100 hours). My experience is that it's usually shaky after 3 days so I charge mine about every other day or so. It takes about 3 hours max to charge up the unit.I have mine linked to my cellphone and also Skype on my laptop. So far I haven't had the chance to switch calls between the two, but the calls on cellphone are more reliable than the ones on Skype. It drops calls on Skype very often and the sound quality is not as good as cellphone.One thing I found very hard to use on this phone is the volumn buttons. Because they're small and rigid, sitting on the top rim of the piece, it's very hard to press it while it's on your ear. So instead of using the buttons on the piece, I just adjust it on the phone, which is more conveinent.Overall, I'm very satisfied with this product. I don't think there is a "perfect" product. Fortunately, all the most important features of this headset (sound quality, comfort) are performing robustly that I'm okay with living with the little flaws it has.