Vance, airspeed stability with respect to power setting or aircraft angle of attack is more a means than an end for our VFR aircraft (it's really important for IFR craft). A LACK of it suggests that something else is amiss. That "something else" may be hard to test for, but may be a hidden coffin corner.
I worry when my aircraft slows up in an updraft, and then KEEPS slowing up aftre I'm through it unless I push forward and dive to regain airspeed. I worry when I add power and the aircraft's nose drops, airspeed picks up and I need back stick to restore airspeed. I worry when I enter a power-off dive and the airspeed keeps building unless I add back stick.
In each of these cases, airspeed is, if you like, an easily measured stand-in for something more difficult to measure -- the net moment on the airframe, minus the rotor.