I have done a little bit of research lately and from what I can tell, it depends on the instructor. Some are good and teach self-defense and others are LARP*-tastic RBSD** shysters. Look for a school that spars full-contact.
I do have one gripe about KM and it is more about the internet guys. They always put down "sport" fighting, like BJJ, Muay Thai, and MMA as self-defense because those MAs were not specifically tailored for "teh 5TR337" like KM. Any Martial Art that spars at or near full-contact is good for self-defense, because if you get a knife pulled on you or multiple opponents, the best martial arts are run-jitsu and glock-fu.
**RBSD=Reality Based Self Defense
"We will not cheat steal or lie, nor tolerate any among us who do."
If liberals interpreted the Second Amendment the way they interpret the rest of the Bill of Rights, there would be law professors arguing that gun ownership is mandatory.