Below is a short intro to an interesting form comparison video.   Matt provides a few thoughts on taijiquan and then has a short video of different versions of Grasp Sparrow's Tail, Single Whip.  The comparison and the intro are both worth taking a look at.  What are your thoughts?

Taijiquan (Tai Chi) is a lot of mindful work. Inside intention and will are on alignment of knee with the foot, open and closing "kua" valley of the hip joint with inguinal thigh. smooth flow, spine straight, expression in the fingers, spirit in the eyes. - Matt Stampe