Having used pepper spray over 50 times in the past 15 years, I can attest to the effectiveness of it when used correctly. The key word is correctly. Most citizens do not have the training in the use of OC and expect magic bullet results no matter where it is sprayed.{Remember, you have to spray the face, preferrably directly in the eyes}
For me, pepper spray has been 100% effective in gaining compliance. I have sprayed bar brawls, drugged up individuals, drunks, even a group of Marines brawling with a group Seamen.
I hear people tell me all the time that it does not effect them, that they have been sprayed so many times that they are immune{OC is an inflammatory, you don't build up "immunity"} but when I offer them $100 to let me spray them with the X2 I carry on a pocket clip,oddly enough I get no takers.{the $100 is if they are unaffected, if they have their eyes slam shut, do the snot blowing thing, and wheeze I keep my $100}
I am also an OC Instructor.OC will work effectively on multiple assailants,but like I teach, OC is not a substitute for leathal force,nor should it be used as such.