I realize this is a little larger than normal, but I think it has more imact in a larger size. Mods - I'll be glad to shrink this down a bit if necessary.

http://canonbob.smugmug.com/photos/149023231-O.jpg

The catchlight is indeed a pinpoint. Great detail here. It appears to be a significant crop as the detail in background looks a little odd. Can you post a full-frame version of this image? I'd love to see how much detail that imaging sensor holds at high crop.

I can dig through my files and post a similar uncropped/cropped image to see some real world comparison between to two sensors.

Here you go (link to "original" size right below it):
http://canonbob.smugmug.com/photos/149670923-L.jpg
http://canonbob.smugmug.com/photos/149670923-O.jpg

Thanks, Bob.

This is the best I could do. Similar subject size and crop. Shot with my 30D and 300mm f/4L + 2x TC. ISO 400, 1/125s, f/9.5, handheld. Uncropped full frame image and its crop.

Kind of a tough comparison at this size. Tell you what, since i own both the XTi and 1DsMII, I'll put them head-to-head at my bird feeders. I'll shoot the exact same settings, and move the same lens from camera to camera for comparison shots. I really don't notice the difference until I get to the details. I'll link to the originals of each for comparison.

Even though the 300/4 is a superior lens to the 100-400 (sharpness-wise), you probably lost some detail with the 2xTC.. I lost some because I needed more DOF to really nail the shot (and a bit more speed too).