I confess that I'm a recovering Yoga Snob.  Since a bad experience at the 24 Hour Fitness about a million years ago, I've avoided large class, gym yoga.  Today, I was totally exhilirated by a Yoga Flow class here at our local YMCA, Merideth Mathews, in Seattle.  I think these kinds of classes need to be chosen carefully if you're new to yoga.  The pace is fast, the class size doesn't lend itself to individual coaching, and the terminology can be confusing.  There are a few beginner classes that the Y offers that would be a better first step.  If you've done some yoga, though, I'd highly recommend checking out Yoga Flow at the Y.  We began with some long, slow stretching and gradually worked into a challenging diverse series of sun salutations, plank, tree, and then a fair number of poses and flows that we new to me.  I'll be back for more!