I bought some a while back but haven't used it yet - it is soooo soft, seems like the fibers are more like silk than cotton. The package warns of shrinkage and advises to pre-shrink by washing and drying before using.
I have heard stories about it being a natural antibacterial, and great for folks with allergies. I guess that only applies once it is inside the quilt. It's not cheap though - I used a 50% off coupon to bring a queen size down to my price range.