Nice shots, Brad. Glad to see the MkIV and the new 70-200 play well together. Also looks like you had rather nice, bright conditions for shooting, and that did not create too much contrast....always a worry.
You cannot be too serious about the heft of that combo, though after a while, it does seem like it gets heavier ;-) (I shoot with the 400/2.8L IS, and THAT is some serious weight, while I have the "light" 70-200/2.8L IS around my neck for close in shots.)
Cannot tell from some of the other shots, but it looks like f2.8-4 may be the sweetspot for bokeh, especially with bright leaves and stuff in the background. hard to get that stuff smooth on bright days.
M5-Guy----it can be really surprising just how thin DOF can be at some distances. I shoot a lot of stuff with the 70-200 at f4 or 4.5, for smoother OOF, and the "penalty" can be one player in focus, the one a step in front or behind being out of focus. You are right about movement also with respect to sharpness. For action stuff, I try not to get below 1/1000 -1/1250 most of the time, unless the subject is moving only slightly obliquely to the camera. I mainly shoot polo, so speed of play and movement tends to be much faster, but stuff like this, football, and soccer have surprisingly quick movements on some plays that are hard to stop or get really sharp without higher shutter speeds.
This combo is in the "replacement queue" for me right now, so it is nice to see some results from folks using it.
LJ