In reply to wobl:
Used a Jetboil in Iceland with temps down to -15C and didn't have any trouble. Shouldn't really be a need for gel packs to be honest as long as you have the right gas. If it's that cold I'd rather use them for myself!
Just keep gas canisters off the ground and warm them up a little before using, and make sure to gradually add snow to melt it rather than just smashing the lot in. No trouble whatsoever*
*except trying to light the damn thing in the wind