Hi Waj, I have used this stove at around 10,000 ft without problem. It seemed to take about 25-50% longer to boil 16 oz. of water.

Having used both liquid fuel and canister stoves for hundreds of meals, I prefer canisters up to 13,000 feet. With canisters, you don't get quite as many BTUs per ounce. However, when you factor in the spillage and priming factors for liquid, I think it's about equal. (I also think the extra ounce for a built in ignitor is worth it, because you tend to shut the stove off immediately knowing it's easy to relight, and you waste less fuel lighting it.) I use the freezer bag food method and only "cook" with treated (Aqua Mira) water. I can easily get 16 to 20 person-meals out of one 8oz canister by cooking on low, making sure there's little heat loss up around the sides of the pot. Your mileage may vary. If you're planning on doing lots of real cooking and/or water purification, then liquid may be worth it. One more canister tip: I agree with the comment about cold temperature reducing the efficiency of the stove. If you're expecting a cold night, keep your canister in the bottom of your sleeping bag, then stick it inside your jacket when you get up, until you're ready to cook.

I have used a canister stove at roughly 10,000 feet and although it works you do find that you are utilizing more fuel due to pressure loss. If you are planning on using this above 9,000 feet I would suggest a liquid fuel stove. It may be a bit heavier but you will save weight by utilizing less fuel and not having to carry out used canisters. I do own this stove though and for a low alt. stove you can't beat the price and weight. Hope this helps.

One of the reasons canister stoves don't work so well in high altitudes is because of the weather. In cooler weather the stove works slower because there is less vapor pressure (warming the canister in a shirt or sleeping bag before use can help). Wind can also become a factor above the timber line. At higher altitudes foods take longer to cook so keep that in mind when planning on how much fuel to take. So as long as the fuel doesn't get to cold or the winds are too high to keep it lit, the stove will work (water will actually boil faster).