In reply to Fraser:
Hard to answer. It's about as windproof as anything else made of pertex, I guess. I've never noticed it not being windproof and I probably would if it wasn't.
I normally wear it with a baselayer under it for cool weather and a baselayer and microfleece for genuinely cold weather (eg cold winter days walking in scotland) or if I'm not going to be moving very fast (eg climbing). Although I run reasonably hot so YMMV.
The pockets are really useful, because they mean you can control your temperature a lot by swapping gloves, hats, buffs etc on or off without having to stop and faff.
I've got the full zip version with the hood and pockets, fwiw, rather than the half-zip without.