Use of all available performance indications
While I continue to point out all the benefits of a HUD that was operational back in 1968 or so, I agree for the most part that we have plenty of information to use when things turn sour.
The thing about our HUD in the SLUF and Viper was it complemented the steam gauges. And since we had a combination of air data and inertial data, it was a lifesaver when the pitot-static system failed. Someone mentioned that the PF could tell he was climbing by using the altimeter. My understanding is that "all" air data was unreliable except AoA, and AoA ( separate probe) was deemed unreliable due to low airspeed. BEAM ME UP! The baro data was FUBAR! So there goes stall warnings and such based on AoA.
When our air data froze, that's what we saw. Frozen scales or blank scales. The flight path vector was still good, as was bank angle for the pitch lines. We could also select groundspeed for display versus CAS or TAS.
Most useful basic use of our HUD was landing in 100 and a quarter. Not that I never did that back in the 60's using primitive steam gauges.