An old friend (whom I regret not having fished with in nearly a year) brought one along on a trip to Lone Lake one very cold winter day. He fired it up with a few sheets of newspaper and a handful of kindling as I recall and we had boiling water in no time. The cool factor for a Kelly Kettle is pretty high IMHO. But the reality is that you also need to bring fuel and matches that need to be kept dry and which take up space.
If your goal is simply to boil water in a hurry and you prefer not to have to mess with the accoutrements of a Kelly Kettle, I'd suggest a JetBoil instead. They're lightweight, compact, and weatherproof. I've used mine to heat up leftovers in a seal-a-meal pouch on the rear deck of my pontoon boat. Not sure I'd want to try that with a Kelly Kettle.
I also think the cool factor is high and have thought about getting one. But, they are heavy and take up a lot of space. There are a couple of lighter, more compact modern versions on the market now, however. One that is getting rave reviews is the Backcountry Boiler. You could easily pack this one not just in the boat but in your daypack on bird or elk trips too. It is new and they are having a problem keeping up with demand but it looks pretty sweet. http://www.backpackinglight.com/cgi-bin/backpackinglight/boilerwerks_backcountry_boiler.html
I have one and have used it for years. It a little heavier than most but it is not a problem in the boat. It takes so little fuel to get water going, I have never had an issue finding enough - even in the rain. I just keep a couple of pieces of crumpled up paper handy and have water in minutes.
Have one and like it. Crowd pleaser. Store a tube of Fire Ribbon in the chimney and you can always find fuel. Damp twigs no problem.
Kelley also makes a smaller version I've considered for hiking instead of Svea and gas bottle.
Is that the "Scout" version, David? It'll hold 19oz or something like that, I think. I have a blast match with some vaseline soaked cotton balls, which work great as a fire starter, too. I hadn't considered fire ribbon, which I've used to get the old Svea going!
Or if you are a gadget-geek too, look for the latest and great wood-fired backcountry stove: the BioLite Camp Stove. Uses wood-fire to heat your cookset, and at the same time, creates electricity to power gadgets via USB outlets.
Patrick, maybe there should be a stove collector's guild! Tell the truth, what I'd like is one of those old red and blue box stoves, Svea or Primus; I can't recall. They were cool! We had one almost 40 years ago, but I have no idea what happened to it.