In reply to RicheyPen:
I work outdoors all year with it, have only found it to be a problem when I have a sudden change of temp, this has only really happened in summer when a route/climb moves from a sunny face to belay in a gully or the shade.
Have found as long as I can maintain a constant core temp; I don't have a problem with my hands or fingers getting too cold, have been up tp 6000m without even contemplating Raynaud's disease being a problem or it being an issue on the trip.