The fabric, color, comfort, and construction is excellent. The only draw back is the metal zippers are a bit stiff and tend to stick, but I having read other reviews prior to my purchase I knew about this. Regardless of the minor inconvenience I like the metal zippers for the style and durability. I love love LOVE my new back pack and I use it several times a week.
Does the Thirsty Yoga towel have rubber on the back to keep it from slipping on the mat?
No, this is only a towel. You should absolutely look at the Travel Mat Gaiam sells here. I love mine it's fantastic. It's thin, lightweight, and easy to wash and care for. It's a light textured micro fiber on one side and rubber on the other.
Can Thirsty Yoga Towels be used alone? Or does it haave to go on the top a regular yoga mat?
Assuming you are asking if it can be used alone as a mat, then I would say definately no if the surface is wood. If the surface is carpet then maybe, but I wouldnt recomend it. I use this mainly as a (folded) cushion towel for my knees and as lightweight and absorbant sweat towel. My friend uses hers to layer over her mat for extra cushion. If you want an awesome thin lightweight mat get the travel mat. I recently bought one and I love it immensesly!