Jeremiah Rozario wrote a review of Jetboil Flash Personal Cooking System on September 30, 2011
Opinion: The JetBoil only has two settings. On and off.
Fact: The JetBoil has an adjustable burner but the control is very sensitive. The knob turns a full turn and a half but the range of adjustment is all within the first 45 degrees (1/8th of a turn) from the off position. The flame will go down to about 1/5th power (estimated) before it goes out.
Opinion: The JetBoil is only for boiling water.
Fact: They do boil water fast. However, an optional pot support makes it universal for packable sized pots or pans. You can use JetBoil for making any meal within reason. It's just that freeze dried meals are the lightest using the least fuel. Hot spots can occur with any backpacking stove due to the cookware. We need light stuff. Heavy cookware can eliminate hot spots but we don't pack it due to weight.
Opinion: The JetBoil is too heavy for ultralight backpackers.
Fact: The JetBoil Sol Ti is 8.5 oz. MSR's Titan Kettle (4.5 oz) combined with a Vargo Triad alcohol stove (.75 oz) weigh 5.5 ounces together with a wind screen. At 5,200 ft elevation, the JetBoil (I used the Zip) boiled 2 cups of water in 2 minutes, 24 seconds consuming 4 grams of fuel. The MSR/Triad combo boiled two cups of water in 8 minutes, 10 seconds (in kitchen) consuming 12 grams of fuel. So the JetBoil will boil approximately 50 cups of water using one 100 gram canister (6.75oz for can + fuel) in 1 hour. The alcohol set-up will boil the same amount of water consuming 10.6 oz of alcohol taking 3hrs, 24min and 10sec. The Zip + fuel weighs 1 lb, 2.3 oz (15.3 oz if the Sol Ti is used). The MSR/Vargo combo weighs 1 lb, 1 oz with fuel. I ran the same test with the Titan Kettle and the Pocket Rocket (same fuel). Boil time was 2 minutes and 20 seconds (in kitchen) but it used 10 grams of fuel. That's 2.5 times more fuel than the Zip. The same test in 20 mph winds at 15 degrees Fahrenheit; the MSR never boiled water, the JetBoil was unchanged. JetBoil wins the weight game through efficiency almost every time.