It worked immediately after plugging. Both on my old MacBook Pro (Mac OS X 10.6.8) and with my new MacBook Air (Mac OS X 10.7.4). No installation required. The use can be adjusted both via Skype as well as on the system settings.
+ Good voice quality on both sides
+ Microphone: there are background noise filtered out
+ Up / down keys on cable
+ Mute button on the cable
+ Fits comfortably
+ Foldable for easy transport, incl. Soft case for transportation
A star deduction there, because the calls for key accept or hang up the installation of an extra program requires that there is only for PC (on the site of Plantronics downloadable). Would buy the headset still again. I highly recommend it.