My most wanted list, anything more to add?

[Daniel Browning]

But image quality suffers when you try to put a high number of pixels into a smaller space

I disagree. In ample light, a small sensor with more pixels has higher resolution than a large sensor with fewer megapixels. The 50D puts out images with more detail than the 5D1, for example. Noise and dynamic range, though, are of course better with the larger sensor (number of megapixels has nothing to do with it).

less light hits an APS-C rectangle than an APS-H rectangle than an APS rectangle

Not necessarily. If you're using the fastest, longest lens you can afford (or carry), then all the systems get the same amount of light falling on the sensor. That's why I brought up sports and wildlife photographers, because they will benefit the most from a 1.6X pro system.

I suspect that's one of the main reasons that the 1Ds3 has one less stop of ISO than the 1D3.

If that were the case then it would be the other way around, as the 1Ds3 with the same exposure has less noise.