Not yoga, but spinning! The one and only class I took at my new gym (lifetime fitness- not mom and pop place) was HORRIBLE!! I know the guy was just filling in, but it was actually BORING! And I barely kicked up a sweat.
I just hate that!
But I must say I've had good luck with the pilates classes they have. Both instructors are very good.
I feel your pain though. Like I said... UGH!