I have Paul Grilley's Yin Yoga
DVD and love it. It's both a wonderful physical release and meditative experience, not unlike Restorative Yoga. The music is beautiful too. I'm not sure how important that is to you, but the soundtrack will make or break a practice for me.
He also offers a "music only" mix with minimal instruction, which is great once you've gone through the practice a few times and understand the poses. Then you can just hang in the pose and quietly reflect without having to listen to the same explanations over and over.
I've eyed Sarah Powers with some interest, but since I have so many yoga DVDs already (that are badly neglected lately ~ Paul's included), I've consistently passed up her Insight Yoga