As many people know, I work at a great facility that purchases products all the time and it is great to have a budget.
http://www.performbetter.com/detail.aspx_q_id_e_4550_a_categoryid_e_219
After a few months I have put in a lot of time using them with various movements to enhance our strength training program and found that they are fantastic. They are not ab wheels, but I use them for various shoulder and core exercises as part of a great warm-up for benching.
The power rings are used by Phelps, the olympic swimmer, and they are great for adding spice to pull ups and pushing movements.
I am working on a PDF for athletes and they are very durable and well made. I get no kickbacks here.