At first, I didn't think this Phoenix Audio Duet USB speakerphone was really necessary — I mean, using a headset with Skype should be enough, right? Well, according to the VOIP-heads over at VOIPSpeak:
a USB sound device is much more efficient than using a soundcard for VoIP applications... With a USB audio device, the device converts the audio into digital signals before sending it to the computer. This results in much better sound quality and compression which can have a dramatic efect on VoIP conversations.
They go on to say that the Duet PCS not only functions as a USB speakerphone, but also has a standard headset jack for even higher quality sound. And because it registers as an audio device, you can use it on any VoIP or IM app (Skype, Gizmo, Google Talk, etc.). Audio specs include full duplex performance, suppressed residual echo, voice level equalization, and equalizer algorithms. Further testing showed that it was easy to install, and worked as advertised, prompting VoIPSpeak to give it a pretty big thumbs up.
Phoenix Audio Duet PCS Review [VoIPSpeak via UberGizmo]