The 100-400mm is very decent lens. Sharp enough for most occasions even wide open. And it's usable with a 1.4x converter and still able to auto focus on 1-series bodies. I enjoyed the dozen or so times that I used it in the last two years. The image stablization was more effective than I expected. The only thing I didn't like it much was the f5.6 maximum aperture in the long end, and the fact that this thing looks intimidating when fully zoomed and with a hood on. I also didn't mind the push-pull zoom either. The lens was sealed well enough that I haven't noticed any dust inside the lens.
The 16-35mm f2.8 II is the second generation of this bread and butter lens for most pros. I owned the original version and didn't know how Canon could charge such an insane amount of money for a lens with such bad edges on full frame. I eventually sold it back to the person whom I bought it from, a year later, and he seemed not to mind the soft edges at all. The MK II is improved, no doubt, but not to the extend that it could compete with the ungodly sharp Nikon 14-24mm f2.8. What's a Canon user to do? Switch to Nikon? For most of us, we just take what Canon offers, unfortunately. At least most users of this 16-35mm lens seem to be quite happy with it, and I am sure I will be happy with it as well. Time will tell.