I have been agonizing over whether to get a 70-200 f/2.8 IS or a 100-400. I don't know if I'm psyched about the push-pull zoom, and I have been reading variable reports on the IQ. On the other hand the 70-200 is a little short for some of my goals, but has universally acclaimed IQ and I think I prefer the zoom ring form factor, in my mind anyway. If I put a 1.4x onit, then I'd have more reach (280mm) but I'd be downnear themax f of the 100-400 native and would supposedly lose IQ. They both have IS, so that's a wash.

I already own an EF 17-40 f/4 L and an EF 28-135IS. Ultimately, I would like to replace the kit lens with a 24-105 f/4 L IS,but I haven't really been unhappy withthe performance of the 28-135, and in the meantime I want more reach. I like to shoot birds and other wildlife, motor racing, and flowers, but I've actually had some success with macroapproximation using my 135 wide open at 135 and close distances, so I don't care about MFD of either zoom. I will also be getting a 100mm f/2.8 macroeventually anyway.

I want to cover the vast majority of focal lengths that I would reasonably use with as few lenses as possible, so I can practically bring them with me when I travel. I also want the best IQ that I can afford.

I have been so impressed with Nate's wildlife pictures using his 400 f/5.6, but it doesn't have IS, and I'm not sure my hands are as steady as his. I would like a lens that can approach that with IS, which is another reason I have been considering the 100-400.

What say ye, owners/experienced users of the 100-400 and or 70-200 f/2.8 IS? Is there really any reason to avoid this lens, or am I reading too much into Bryan's and some others not entirely overwhelmingly positive comments and reviews?