Totally agree: These are expensive machines and cost a fortune to run. While many people love cooking on them, others complain that the cooking function is primitive at best. To get different temperatures you need to move things around amongst the different plates and ovens. The left hand sides of the ovens (facing the burner) are much hotter, so food needs to be turned frequently. If you cook a large meal the heat drops, and so if you need a very hot oven to do something at the end of the cooking session (biscuits, for example) you'll find yourself out of luck. A family friend has one, and I've used it, and like it. But it takes some learning to get it right.
If you love the looks and want one just get a cooking only regular Aga and an Aga cookbook to learn to cook efficiently on the thing (key is to do as much as possible inside the oven). The Martha Stewart video is totally unrealistic, you cannot cook all that food in an Aga in a single day, the stove loses heat as you cook and takes a while to heat back up again. Even big pots of boiling water for pasta can do you in; people talk about bringing the water to a boil, shoving the covered pot into the simmering oven for an hour or two, then putting back on top to boil up the pasta, thus allowing the top plate to get "recharged" as it cannot bring 5 quarts of water to the boil and hold them at a boil for the necessary 15 minutes.
People in the US who are running them on propane have fits over the cost; I think I read that they use 50-60 gallons of propane a month, just for the stove. Really absurd. If you're on natural gas, the cost would be more reasonable (63 therms per month) but that usage, for cooking, is really silly. I bet my heavily used, pilot ignition, 6 burner/two oven kitchen stove doesn't use that much gas in a year!
But... we have a large, cold kitchen, and probably someday when the funds are there I'll go ahead and have an aga installed. We only live once!