After some delays with shipping, today I finally had all the parts to take the MK II out for a spin. MK II, B20 grip, two LP-E6P batteries, all wireless turned off, using the RF600 f/4 w/1.4x. After some initial tweaks on the AF and the sun became more consistent, switched to precapture and got a few flight sequences. Took about 2100 shots of chipmunks, birds and a bobcat, with the batteries showing 50/51%. The precapture definitely adds some bonus shots. Overall much faster focus lock and it stayed stuck on the desire subject a majority of the time. The afternoon was at the river and there was a lack of subjects. A pair Reddish Egrets in the distance then had a Tri-colored Heron fly over and pose, really too close, then a few sequences with it fishing before it followed a Snowy further down the river. Did some other flight shots and noticed the rolling shutter with the background is effectively gone. My initial take is this is definitely an improvement over the original. May try some video tomorrow but that's never been a priority for me.