As to focus shift: it only happens when stopping down, not wide open, and only up to about F/2.8, and between MFD and a few metres, and again, only if it hasn't been calibrated properly.
It is a magical lens indeed, and more than plenty sharp; it actually is very sharp, even does very well at macro distances with a few extension tubes.
Rendition and OOF blur behind the focus plane and in front of it are extremely good; I haven't found a lens that can match it bokeh-wise, although I haven't shot with any of the longer L-primes yet (200 F/2 L and up). Hmm, maybe some of the TS lenses do as good, but those require a different mode of shooting.
Do note that good bokeh in front of the plane of focus is contradictory to good bokeh behind the plane of focus from a theory POV. It si truly amazing Canon managed to get both right in a single lens.
I just love it - my main go-to lens.
Kind regards, Wim