However, in some of the skies where I fly, London TMA, Western Europe etc., when the airspace and the RT are so busy; hand-flying would add an unnecessary layer of potential for f**k-ups. Folk can say that PM should be able to deal with PMing even if PF is manually flying, but I would question the wisdom of doing that and possibly overloading the PM, and let’s be honest the PF too, in very busy airspace. So one would have to be sensible.
Indeed many are, and in such TMA's many operators advise the use of A/P soon on departure. Busy radio, lots of traffic on MAP, step climbs etc. So why do some operators still insist on manually flying that rare manoeuvre and often messed up, the simple GA in the very same airspace they advocate A/P SID's? Seems contradictory to me. I've heard tales from colleagues who made GA's, in crowded airspace, with low level off and 3 different 'official' GA's. The FMC was programmed for the correct one, but non-radar tower was demanding to know the reason for the GA and also giving navigation to a different beacon and a freq change all while manually flying and trying to clean up. Safest SOP's? Hm.