In reply to duckman:
Which Atom, the SV (now renamed I think) or the LT? I have the SV which is more a warm mid-layer/light outer than a thick winter belay jacket as it has 100gsm of Coreloft. Nice jacket though and I use mine in conjunction with thick base layer, a non membrane softshell, a Polartec Alpha hooded top, and a light waterproof as part of a winter layer system rather than having a heavier belay jacket.