I bought it years ago and it did help a lot. What helps even more, and more permanently, is making sure your chair and sewing setups are ergonomically correct.
Nancy's Notions price seems high, even on sale. I found it on Amazon for less:
http://www.amazon.com/Therapy-Best-B...dp/B001F0G5CQ/
Also found it at Overstock for less:
http://www.overstock.com/Crafts-Sewi...8/product.html