I was pretty deep into kickboxing for ten years. Took a year of shotokan karate in the army and quit, as it was not violent or realistic enough for me. Went back into kickboxing, and loved it. Got good, but like most hobbies, it made way for others like cars, shooting, and softball. Then I switched units, and my boss was pretty deep into it. Which is where I got enlightened to it for the first time.
After that, the army started teaching it to us, for hand to hand tactics. Then it became widespread.
Now most of my buddies take it, and I roll with them on occasion. No matter how good of shape you're in, it will wear your ass out GOOD. It is a GREAT workout, and I recommend it to ANYONE looking to get into shape, and/or lose weight.
Regardless of weight/strength, it is a great equalizer, and a great way to defend yourself. (a 1 on 1 deal anyway) I've seen many big dudes, get locked up by smaller, quicker, more skilled opponents.
I am looking into taking it formally, but I too, have limited time. I wish I had more free time though, as I would LOVE to take it seriously. It's VERY fun, and is a no excuse form of competition.