Thanks for the links AlanF. I am not sure I trust the opinions of these reviewers re the acuity at 800mm. The couple of actual image examples are showing subjects at the long end smaller than the subjects at the short end, which says the distance was more than 4x. Concurrently, there is no mention of atmospheric contribution and having spent a lot of time at 800mm and above, I am very cognizant of how rarely conditions allow long shots that fully demonstrate the capability of an 800mm lens. I find that quite often, the 800 f/11 will produce results that are comparable to the EF 800 f/5.6 L and that is not because the 800 f/11 is an equally good lens, but rather that it is better than the air on that day (so to speak) and thus the big L shows little or no gain. If conditions are right, the L wins by a fair bit. The 200-800 MTF curves place it between the two lenses I have, but a bit closer to the 800 f/11, which makes sense with diffraction corrected MTFs. The big deal is that the MFD goes from 19 ft on both primes down to just under 11 ft on the zoom and that results in more magnification of small subjects like my resident hummingbirds. Max magnification on the primes is .14x and on the zoom .2x (at 800mm). All else being equal, that alone was enough to convince me to preorder the lens, but the zoom is also a big deal in many situations.