skypeenglish at lists.tffppodcast.com (Michele Barbi via Skypeenglish)...
Ok I tested on my USB headset which I think I never plugged on my Mac,
and was able to make them work.
At first I have to say that my Skype is configured to use the system
settings for microphone and speakers. As soon as I plugged my headset, I
could hear even VoiceOver from the pc speakers. So I went to the system
preferences, sound panel, and I was able to configure the USB headset as
default device, answering yes to the confirmation request which popped up.