I took these free TKD classes a few years back. They were hilarious. I pretended not to know anything about fighting in order to go along with the horrible chambering they made us do when kicking. I accidentally did a Muay Thai straight out of habit on the instructor when he chose me for a sparring demonstration and he fell backwards. Another time, this girl who stood behind me actually laughed at the "hiss" I made when striking. I guess I can't blame her since only posers like Muhammad Ali and Mike Tyson are known for proper breath disbursement. She declined my invitation to go a few rounds, funnily enough.
It can be of benefit in cross-training, especially through the flexibility that you'll garner, but it's easily the most McDojo'd art around.
Also, my friend is a third degree black belt in TKD. I place zero value in belts, but I fight him pretty regularly.