Rich and Rick -
My previous wildlife camera was the 1D Mark III, and while it does have the 1.3 crop factor, the quality of pixels is quite a bit lower than the 1DX. So as you suggested, I can happily crop my 1DX images by a factor of 1.3, and they still look better than a non-cropped image from my 1DIII. As a result, I'm getting the best of both worlds --- wider angle photos that I can crop when I need to. I have to say, I really (really) like the light weight of the new 500. It is 1.5 lbs lighter and 2.5 inches shorter than the 600 f/4, which is significant. Handholding is quite important for me and this lens is wonderful for that. The new 1.4 TC works brilliantly, so if I'm going birding I can slap it on and get all the length I want. I suppose there are always times when more focal length would be good, but for me there are more times when the wider angle is nice (shooting bears for example).
Hope that helps!