Thanks. The secret is a couple well-placed RSS feeds and a substantial amount of selection. The truth is that /randompictures/ and /r/pics/ both produce content at a rate far greater than I could ever post. To wit:
Salty is right. The 70-200 F/4, in both IS and non-IS is sharper and has better color transmission than the 70-200 F/2.8 (IS or non-IS). The 70-200 F/2.8 II is currently Canon's sharpest zoom. It has pretty impressive color transmission, as well.