Nice photos, Ellis. I've been shooting the Canon 70-200/4 for a couple of years, and it's one of my favorite lenses. I take the f/2.8 version only when I absolutely need the extra speed, which is not very often these days.
I'm starting to think that the f/4 zooms do 80% or so of my work, and the fast primes do the rest, leaving the f/2.8 zooms heavy, expensive, and not as useful overall.