In reply to UKC Gear: I think it would be worth mentioning speed somewhere. I've climbed for years and only rarely had to set up a hoist system and even though I know what I'm doing, it takes a little time to set it up. If your casualty has fallen down a crevasse and is up to their neck in ice cold water, even a minute or two could mean the difference between life and death.
Also, if you are self-rescueing and you are wedged in a narrow crevasse rather than hanging free, this system is going to be the muts nuts (assuming you can get your hand to your harness to unclip it).
I can imagine if you are a certified mountain guide you wouldn't have much truck with this kind of thing because setting up anything with the available gear is absolutely second nature but I think aside from the real professionals, most people would benefit from the convenience and speed of using it (no I don't work for Mammut sales dept
).
I don't think the average novice, under the pressure situation of having to rescue someone would be able to just come up with a functional hoist system after a few moments of thought. I think that is rather like saying "I'm sure someone who has only ever waded before can swim if we throw them in the deep end", if I was the novice, I'd rather have the arm bands... ahem... rescue device.