The "1D" cameras are a series of heavy, expensive, no-holds-barred cameras that Canon offers as the flashship cameras in their line.
The 1D cameras are a world unto themselves. They have massive bodies with dual grips, and the first of them at least were designed to have the same control layout and interfaces as their professional film camera, the EOS-1V (which was still in production in 2007). The controls were revised significantly with the 1D Mark III, and I have found making the transition from a 5D Mark II to the 1D Mark III to have offered no big surprises.
The bodies are sturdy, heavy, and carefully weather sealed. They are, in particular, designed for rapid (as fast as 12 images per second) image capture. If you are a professional sports photographer, you will want one of these.
Well, perhaps the wildlife photographers are upset. They appreciate the extra reach that a crop body gives to their lenses (like a built in 1.3 or 1.6 teleconvertor). They will either need to use the 7D camera, or crop what they want out of the 18 megapixels the 1DX gives them.
Canon 1Ds ii shutter life statistics
There was apparently a serious problem with the autofocus system on early versions of this camera. Canon apparently completely redesigned it and you do not want an early version of this autofocus. They for all practical purposes did a recall of the camera and replaced the system for free for people who wanted it done. Cameras shipped with the new autofocus are said to have a blue dot or square next to the bar code on the camera.
Canon 1Ds ii shutter life statistics
I am particularly gratified though that Canon seems to have realized that the game is not all about more megapixels. People are excited about the 1DX because of its high ISO performance and superb image quality. For this class of camera (which outperforms 35mm film cameras and begins to rival medium format), something in the neighborhood of 20 megapixels is plenty. 18 might be almost perfect (easing off a bit on file sizes and disk requirements). People are making excellent 24x36 prints from these images, or at least they say they are, and that is as much or more than what I ever aspire to do.
I particularly like a quote by Art Wolfe about when he first was using a digital camera:Remember, this was my first time shooting with digital and when I was able to bump up the ISO to 400 and capture a decent shot of the seal while bouncing on the waves and then try another at 800, I was sold. I never loaded another roll of film again and I came home with 300 rolls of unexposed slide film, that I sold the very next week.
Tom's Digital Photography Info / tom@mmto.org