I made my first Skype call to a POTS phone today. I had a bit of trouble getting the PBX on the other end to recognize Skype's touch-tones to enter the extension to the person I was calling, but other than that it was perfect. Sound quality was flawless on both sides, not a bit of noise in my headset whatsoever.

I used Skype because my land-line was in use. Since I have a flat-rate-anywhere-in-the-USA-or-Canada long-distance plan it's unlikely I'll use Skype regularly, but it's great to know it works so well when I need it.

FWIW, I used my Logitech USB headset on my PowerBook to make the call.