Yeah, Ali Q has it right. Although he will now be beaten close to death for revealing one of the F4 Pilots' secrets. There is no 30 year rule for some of the truly important State secrets.
Anyway, she (the F4M and K) was OK in benign flight regimes without the Stab Augs, just a tendency to hunt a bit in pitch and a lot more secondary effects of controls - I just put that in so the QFIs will think I really did listen to them.
Manoeuvring was a different thing. She would bite your bum if you mishandled her WITH the Stab Augs, way more so without them.
So, back to Ali's little indiscretion. I climbed into the back seat of an F4M at A secret Lincolnshire F4 base in the early 80s to go and fly my first IRET. (Back seat instrument rating and qual as an instrument rating examiner in case you care). Long story short, I was given a port engine failure straight after take off and a diversion to a nearby airfield. My man turned off the Stab Augs. It sucked a bit on a check ride, but was OK. The bastard was that he refused to reset them for the rest of trip. Presumably just for fun - his, not mine.
Bottom line - we weren't doing combat so it wasn't a huge deal. It did make a difference, but it wasn't a big issue in that benign regime.
Contrast: 1v1 doggers, electrical transient made all three channels trip out (assisted by some very heavy-handed pilot inputs). Now that was very different. The clue is in the name - stability. I guess it was actually flying the aircraft and, therefore, a great lesson in what an unforgiving lady she could be.
MacAir wouldn't have put the system there if she didn't need it.