As for me, I carry one of three guns primarily. Glock 23, XD .40 Service Model, Kahr CW9.
In all honesty, I shoot all of them very well. I don't feel under gunned when the CW9 is carried and I don't feel particularly better armed when either the G23 or XD .40 are on my hip. It all has to do with how well I can shoot the gun, how accurately I can place shots as quickly as possible and how comfortable I am with any particular gun.
It is good that Rob as a high profile instructor is willing to admit he has had a change in heart about his carry caliber and that he explains why he changed. It doesn't mean that anyone should dump their .40, .45 or any other caliber carry guns and run out and buy a 9mm. Carry what you are comfortable with and what you shoot well. I don't see why some feel the need to beat up on Rob for writing this article.