Today was the first day I've really had a chance to use the replacement Mk3 in earnest. I've been shooting MFDB the last two weeks.
All is not as well as I'd hoped, but I'm going to put up with it.
1. While alignment is flawless, there is some discrepancy between what I am seeing in the viewfinder and what is on Live View/Captured File, namely, in a tightly framed scene there is some clipping across the bottom of the frame. So, with critical compositions it is necessary to use the Live View to be sure you're getting everything you want in shot.
2. When shooting a uniformly lit subject against a white background I noticed that there was a faint shadow line across the bottom of the frame. This had all the hallmarks of an incorrect sync speed, so I set this shutter to 1/200 (instead of 1/250). Still the same problem, though the shadow line was fainter. At 1/160 it was fainter still, though still visible.
Only at 1/125 sec. and longer was there a clean image. So, unless I have set something incorrectly in the camera (suggestions on a postcard please! ) my camera does not sync as claimed. Annoying, but not the end of the world. I guess they'll never get this camera quite right.
By the way, anyone wishing to try to test for this will easily see the shadowing on the camera's screen (make sure the the white wall, or whatever, is evenly lit) but, you can confirm it using ACR's colour picker.