I took tae kwon do for about 11 years. Got my second degree black belt. I ended up quitting so I could focus on football, and I think I learned more about fighting through football than tae kwon do. Tae kwon do gave me a lot of discipline and kept me in shape and its one of the best things I've ever done for myself, but its the art of self defense. I can say that nobody can really kick my ass...but that doesn't mean I can kick anybody else's ass either. I also took judo which was more throwing and wrestling...I felt like it was more practicle than tae kwon do. Capoeira is cool and would be a good skill to know, but in real life you wouldn't dance around someone and do backflips. You'd probably just bullrush them to the ground, outwrestle them, and start pounding them in the face.
One of my best friends was a korean kid born in hong kong. He could speak korean, mandarin, cantonese, and english. He took all kinds of martial arts, including tae kwon do. He always recommended muy thai. From what I've seen, it really shows you how to focus your energy and throw some powerful hits. Its one of the most effective fighting styles I've ever seen. He knocked the boxing bag off of the chain with one kick. It was a pretty cool thing to see, definitely seemed legit.