Thanks guys.

With the TC it's not as obscenely sharp as the 400/5.6, but with winter (such as it is) around the corner and the light getting darker earlier, I felt I needed something with stabilization -- I figure I'll get 2-3 stops from it, and with the lens "naked" another stop (f/4 vs f/5.6). As much as I love the 400, it needs a lot of light! Would be nice to have in-body IS like you guys get, but for some reason neither Canon nor Nikon are doing it even though the rest of the competition is.
