First of all yes, Thumbs Up for Logictech USB heasets!
And about your question Wicked you have to set your speakers as default in Windows before entering SL. To do that, right-click on the little speaker icon on the bottom right bar. Then choose Playback Devices and in there set "Speakers" as the default (not the Logitech Headset). Then, once in SL, you have to change the device in Preferences for the chat (located under "Audio - Video". In there, select your headset as the device for voice instead of "default". This way sounds and music will play on your speakers but voice on your headset...
Oups :manvery-happy: