I did for awhile a few years back. Like Twilight Sky, I just sort of jumped into it with no knowledge about it whatsoever. Suffice to say, I lost a lot of battles but learned just as much along the way. What had seemed confusing to me before, started to make sense and became easier to do. Before I knew it, I was strategizing teams, EV training, and breeding Pokémon like a madman making sure I got things just right. I also started trading a lot more and watching a ton of competitive Wi-Fi battles on Youtube.
Eventually though, I just grew tired of it and bored. Competitive battling started to become nothing more than rinse and repeat with people. The Pokémon used were less of a surprise since almost everyone used the same Pokémon for it.
So that's when I just took a break and tried, emphasis on tried, to focus my attention on using my newly acquired competitive skills for the Battle Frontier challenge. At least here I could expand the variety of Pokémon I could choose from. It was fun for awhile, but then I got bored of doing that too. Haha.
I guess I could say competitive battling just isn't my thing anymore. Although, I do like that Gen VI should certainly change the rules of the meta game for people. I, however, just don't see myself getting back into it again. However, I don't plan on letting the skills I learned go to waste in-game. It's certainly helped me become a better player overall and for anyone who hasn't ate east tried competitive battling, I'd urge them to give it a shot. It doesn't take too long to learn the ropes of the meta game.