* Smaller and heavier then I anticipated. Heavy enough that I wouldn't want to use just a hand strap.
* I don't like that MF is disabled in AF and AF+MF (until after you AF and only while you hold the shutter). I realize the ring is electronically coupled, but I want a custom function where I can set it to always work if the camera is on. For that to be practically usable I suppose we would need to be able to move AF off the shutter button. That's fine with me, it's how every SLR I own is setup, and that red dot button isn't doing anything useful in still mode.
I frequently carry my 1D X + 24-70 II by just the handstrap.
You can set the M up with back-button AF (the * 'button') with C.Fn-5.