...just some observations out of 'daily life':
@ mach-buffeting: Experiencing Mach buffeting is common in normal operations: even within the normal speed envelope some transient speed-overshoots happen and buffeting is felt, although I didn't voluntarily fly into overspeed and don't know if it becomes much more prominent if doing so. I even think buffeting is (very slightly) noticeable once your speed goes beyond 0.84, which is well within the envelope....
@ stall-warning: Part of the last recurrent training was an unreliable speed-exercise (actually embedded in a 'flight into volcanic ash'-scenario including dual engine-failure, electrical emergency etc
dunno how realistic the scenario/the simulation is: what really, really bothered both of us was the stall-warning which was not possible to be cancelled, although we definitely haven't been in a stall (thinking about it, it might be a deficiency of the simulator, since if it was AOA-induced, it could not have been valid, as there was no speed on the speed-scale, it should have been rendered invalid by the system): what I wanted to say is, that the permanent yelling of 'STALL, STALL' was so distracting that it almost made us agressive... not good if you have to think 'out of the box' and take decisions in ambigous environments...
@ PNF observing PF-stick-inputs: You do have to focus your view to PF's sidestick if you want to determine what he is doing. Given a scenario (Airbus SOP!) where the PF cares about flightpath and R/T and PNF cares about systems according to ECAM or QRH (and in this situation the main workload lies with the PNF!) there is not much monitoring-capacity left....
It's those situations where I miss the flight engineer most: A guy with intimate insight regarding the systems and some distance to the actual 'haptic' flying: BTW: both prominent examples about rescued airliners where pilots had to 'invent' flying to different rules than trained (Sioux City DC-10 and Baghdad A300) had a flight engineer, but that be only an outdated rant...
In so far, the situational overview of the captain once in the cockpit observing the both F/O's from behind might even be helpful solving such a situation...