When I first heard about underwear made of wool, I was a little sceptical. Then two guys I met in Lappland last winter told me how much they love theirs. I got a 200d top for birthday and had the chance to test it on a 2 day trip last week in quite different conditions (from sunny heat to -14ºC snow storm).
The result: I'm completely impressed! It keeps your sweat away from your body when you haul your pack up that steep path and it keeps you warm even when wet afterwards. Also makes for a very comfortable underwear in the sleeping bag. Short: I love it, get one!