In reply to UKC Gear: For all those wondering about cold weather use on this stove - here's my experiences.
I've used a Jet Boil, and a Reactor extensively. Last year on expedition I used a Reactor at low temps and high altitude (-15 at least and above 6000m).
As with any gas canister design, you need to try and keep the gas warm prior to use, either in your jacket or sleeping bag, or at least off the snow in some way.
I've had great success with the Jet Boil (which is better for hanging IMO, and is what I would take big wall rock climbing) and also great success with the Reactor, which works slightly better in the cold IMO.
Both are great stoves, and both work well. I have seen friends make heat transfer systems for these sorts of stoves in the past, but this could be very dangerous and I couldn't recommend it publicly, however it makes a big difference in cold temps.
Anyway, what is exciting - I think - is the new Joule Stove, as this has a form of heat transfer system built in - check out the UKC report here:
http://www.ukclimbing.com/gear/news.php?id=5666
One last thing. I would take either the Reactor or the Jetboil on any alpine route over a liquid fuel stove every time personally. Unless getting gas canisters is an issue, which it can be in remote places. Also liquid fuel is cheaper, which is a concern for some.
Hope that is useful.
Jack