Actually, I just discovered a problem with one of my M66's recently, something I wouldn't have discovered with dry firing. For what ever reason, the cylinder stop had worn down over time, something that may have been induced by, and possibly accelerated by dry firing. I suspect it was a soft MIM part, but either way, I wouldn't have been aware of the problem by dry firing alone.
Another example of this occurred a few years back with a different K frame. In that circumstance, the main spring had weakened and was producing light strikes, something I wouldn't have been aware of by dry firing alone. The sensitivity difference between CCI-500's and 550's was enough to cause light strikes with the weak main spring.
Both of the above issues didn't occur with lower pressure practice loads, only with full tilt self defense loads. So IMHO, it's necessary to run the ammo I intend to carry, not all problems will present with low pressure target or practice ammo. My life depends on knowing that my firearm and ammo both function flawlessly, dry firing doesn't always expose serious functionality failures or issues.
GS