Pros-Soft base is very comfortable
  -Very hard to stand still in (I guess that is where the calorie burning and increased muscle use come in

Cons- Edges of brown multi-color piece scratchy-  I am hoping that breaking them in gets rid of it

Possible con- Although these should be good for my knee.  I am afraid that it may add too much torque to the weak ligaments in my left knee.  It hasn't happened yet, but I have only been wearing them for a few days to break them in.

Edit 11-2010  These became my most favorite, comfortable and most worn shoes this summer. I bought more brown clothes just so I could wear them more.  The scratchiness went away after a short period of time.  They never hurt my knees once, I think they actually helped them.