The quality of any martial art depends on the skill of the instructor. When you have an unskilled instructor that got their black belt or whatever teaching designation you choose as a kid from a McDojo, as an above poster so eloquently put it, then it does not matter what style you learn, it wont be worth anything.
Any martial arts that gets popular eventually falls prey to the McDojo bastardization. Judo, Karate, TKD, and now we are seeing it with JJ, BJJ and MMA style fighting systems. Because its popular every gym has "classes" where they don't teach you how to defend yourself, they teach aerobics that looks like martial arts.
Its unfortunate and dangerous, because some kid bragging about their Black Belt or whatever is liable to get their ass kicked by a bully. I know too many people with Black Belts that don't know how to defend themselves. They went to schools that taught through line drills, patterns and other training tools and never sparred. Or if they did it was point sparring with breaks after every point so it was completely unrealistic.
New Car: 2008 335xi Coupe
Earlier Car: 2004 STi (got stolen)
Earlier Earlier Car: 1995 Mustang GT (416 whp and a blown engine)
Really Much Earlier Car: 1988 Mazda 626 TURBO