Guy, you need to watch the Tammy. It is very impressive in some ways but it has some bad habits.
First, bang it on a tripod and shoot a test target at 70mm and fairly close range. Focus in LVAF at 2.8, switch to MF and shoot frames thru f8 to see where your focus shift takes you.
Then assess for AF fine tune but be aware that many users have found that this is veeeery complex with this lens. Mine needs different amounts at different ends of the zoom AND it tends to front focus up close and back focus at distance.
Then shoot a VC series (ten on, ten off, middle distant target at f8 with MF unchanging, 70mm and shutter speed around 3x focal length). You will probably find after a lot of messing that if there's enough light at low ISO to keep shutter speeds safe, turn VC off. It seems affected by shutter slap and though some say shooting in Quiet Mode is best, I am veering towards keeping it off unless shutter speeds drop below 1/40th.
That is clearly a real bummer, but mine is for emergencies only and a lot of people seem to have found the same thing. I'm still playing to find the optimal strategy.
Finally, check you aperture lever calibration by stopping down from f2.8 and seeing that the Ev implied by the aperture change is appropriate to that aperture change. This is another known issue.
For all the above reasons I was going to return mine on day one BUT my 24-120 had a failed fix recently and I'm off on a trip so the Tammy is the preferable of two evils. Added to that, it is astonishingly sharp even wide open on centre when correctly focussed, the focus shift is within what I can live with, the AFFT issues similarly aren't terrible.
Bottom line, with a tripod or fast enough shutter speeds, focussed in LV, it is pretty damned good, and with VFAF it's not actively bad, you just won't get it's best.
Mine has softer edges at 24mm than my 24-120 but way better edges at longer focal lengths. It's a mixed bag and I am not yet sure if I would prefer it to a totally optimal 24-120 but there's a good chance, once I really get used to it, that I will....