Interesting topic! I remember on the older models the transient was so loud that it was very common that the captain will say just before shutting down the engines:” Mind your ears.” Basically we will remove our headset just before engines shut down to avoid the painful blast. The spurious ECAM warnings were common also. One of our old A321 was unique on his kind as it will very often have a “Stall Stall” aural warning during engines shut down. Now we only have NEOs and fairly new CEOs (MSN 4000+) All of them the transients are smooth.
Fun fact since Lantirn talked about the APU fire test:
Did you guys notice the warning related to the APU fire test during aircraft Setup in the last version of FCOM?
WARNING The automatic shutdown of the APU and the discharge of the APU fire
extinguisher bottle may occur if the flight crew presses the APU FIRE
test pb for more than 3 seconds.