Never signed up for a class but I've done numerous videos, some along with my wife who is extremely good at yoga.
I've given up on any benefits from yoga, other than watching my wife. I lift weights as well as bike ride and find that the weights have more effect on my flexibility and mobility than yoga. (For the doubters, try squatting over 300 pounds without being flexible and mobile.) Front squats, bent presses, and kettlebell get-ups, among others, really help me.
Just another perspective.