I don't know about Yoga, but I'm very flexible to begin with. I stretch alot. I can do splits front-to-back like nothing once I'm warm, and going out to the side I'm almost crotch-the-floor.
I find being so flexible to be a bonus of anyone who's not, especially if it comes to a fight. Being able to perform those splits proves extremely useful when it comes to kicking.
If you have the time and money, try it out.