I have been wearing rocker-type shoes for over 6 years now (first MBTs, and then Skechers Shape Ups).  I suffer from arthritis in both knees, and prior to using rocker type shoes I had severe debilitating plantar fasciitis.  This type of shoe has made a world of difference for both problems.  My plantar fasciitis is gone now, and the arthritis only bothers me occasionally.  Skechers Shape Ups are way less expensive than MBT shoes and their sizing seems to be more consistent.