I had these rings on my old Stumpjumper. That was years ago.
Probably accomplishing the same thing though (riding in a way that is better for the knees), going to shorter cranks has been a better way to go for me and it's not difficult to do when buying a new bike--e.g., if OEM on the bike is 175mm cranks, you can easily swap out the cranks for 165s without incurring much if any additional cost.