Well I don't do Yoga anymore, but I did see a Yoga teacher privately for a back problem which was completely cured in six sessions, after 18 months of physio failed.
My Teacher started Yoga after a car accident left him in a wheel chair and told he will never walk again, he spent 6 months with a Yoga Teacher in India; he now runs or jogs everywhere he goes, and puts his body in positions I did not even think was possible let alone legal.
So yes it is worth while, but if you are going to take up Yoga because of a medical condition, either go to a Teacher specialising in Yoga for injuries or at least talk to your Yoga Teacher about your problems before attempting anything!!
I think Yoga is a great all round therapy, for the body and the mind!! and I ain't no hippy!!! but I must admit, I have eaten lentils!!