Yoga is a fantastic way to exercise, and in my opinion, leads to a greater overall quality of life. I gives you a great core workout and can be strengthening as well when done right. It helps with posture, and greatly improves flexibility, which is always a good thing. Possibly most importantly is that training of the mind that goes hand in hand with the ancient techniques. Through learning to discipline your body, you also begin to discipline your mind. I have been practicing yoga for 3 years now, and have a pretty substantial ability to calm my mind, no matter the time or place, and that is more than enough to make it worth it.
I would encourage you to give it a shot, you can be the most inexperienced and inflexible of beginners and still reap benefits from the practice. Nothing to lose but some sweat.