Fishmonger,
With almost any brand of canister gas, you're going to get significantly better cold weather performance if you use the canister upside down. However, some brands of gas are better than others.
If you're interested, I've got a blog post up that discusses which brands (by name) are best for winter use:
What's the Best Brand of Gas for Cold Weather? I've also got a list of a lot of the brands of canister gas and their prices:
Fuel Price Guide (Dec. 2011) . Those prices are all from the Los Angeles area, but they ought to be fairly representative of what's out there.
HJ
