Well, you all seem to be falling over yourselves to congratulate Sean Reid on a well balanced article, so I'm going to provide a counterpoint.
I feel a bit uncomfortable with the evidence Sean has provided to support his claim that the camera does matter. His argument is basically anecdotal and essentially, "I know of a number of artists; musicians, composers, painters and photographers who considered that their equipment did matter, therefore it must be true, ie. the camera does matter".
Looking at this from an more objective perspective, it might simply be the case that artists are as gullible as the rest of us in this respect. They hope to gain some sort of undefined advantage from better and more expensive equipment. Maybe it's a status thing, like living in a house that is bigger than we need, or driving a luxurious car capable of breaking the speed limit twice over (if not three times) to get us from point A to point B.
I've read anecdotes about the practicing habits of great pianists, from those living in close proximity or even in the same house. Sometimes they don't give a stuff if the piano is even in tune, yet when they are on stage, they will often make a big fuss about the tuning accuracy of the instrument they are using, sometimes even bringing a piano tuner on stage, in between pieces, to provide that miniscule touch-up. It's called showmanship.
Surely we all know, at least those of us who appreciate classical music, that the greatest music ever written and never yet surpassed, the music of Bach, Mozart and Beethoven, was all written using very inferior keyboards by modern standards.
The availability of the modern piano has not necessarily given us music more sublime than a Beethoven piano sonata.
As far as I'm concerned, the case that the 'camera matters' is not proven. But of course, we should be clear about the context of such arguments.
For example, if I were to say, 'I'd like to take some photos but I don't have a camera', then any reply along the lines, 'it doesn't matter... period', would be plain foolish. You can't take photos unless you have a camera.
Likewise, if I were to say, 'I'd like to photograph that small bird sitting on a branch 200 metres away, but I don't have a telephoto lens', then the response 'it doesn't matter' would be incomprehensible unless the respondent were to add, 'I've got a telephoto lens. You can borrow mine'.
What amazes me is that so many of the arguments opposing Ken Rockwell's statement that your equipment doesn't matter are along these lines, ie. you can't shoot distant, small wildlife without a telephoto lens. Do some people really believe that Ken Rockwell doesn't realise this?
The fact that Ken has a lot of gear, both Canon and Nikon equipment, much of which he has tested and compared, should be a clue that when he makes this controversial statement, 'The Camera Doesn't Matter', he is referring to the artistic merit of the resulting photo, not the technical merit.
To elaborate on this point, if you don't have a telephoto lens with you when out shooting, then there will be certain subjects that are not possible for you too address. Taking close-ups of small wildlife at a distance will be out of the question. Everyone understands that, surely.
Consider the following parable. Three people go on a day's shooting. They all have equal artistic talent and photograqphic competence. One has a 1Ds3 with a standard 50mm lens; one has a 40D with a 500mm lens, and one has a 5D with a 50mm lens plus a 500mm lens.
The guy with the 1Ds3 and 50mm lens will shoot different subjects to the guy (or gal) with the 40D. However, the results of the day's shooting should be equally impressive in their own right, although the subject material will be different.
The guy with the 5D and two lenses might be in trouble. He sees an opportunity for a distant shot, but by the time he's fitted that 500mm lens to his camera, he's lost that narrow window of opportunity. Never mind! He hangs around at the scene for a while, waiting for another opportunity, loses patience and, seeing a wide angle view that catches his artistic eye, decides to change lenses. But once again, by the time he's changed lenses, the lighting has changed and the wide angle shot is just ordinary. Too bad! I guess he had too much equipment.