I normally wear a 6 in women, but I needed a 6.5 in these shoes.  The short toe box combined with the rocking motion meant that my toes were constantly rubbing the front of the shoe while walking.  I over-pronate (flat feet) and I didn't have any problems with ankle rolling (left-right) or being unstable in general.  Be warned that people with smaller feet will roll more (forward and backward) because the thickness of the sole is the same whether you buy a size 6 or a size 10.  I would definitely NOT recommend running in these if you have small feet.

I'm kind of agnostic to whether or not they work for cellulite and toning.  I work out regularly and wasn't sore at all after wearing these for a full day.  I do think that these would be a really great idea after wearing heels, to stretch out your achillies tendon (and prevent planar flasciitis).  And I definitely feel that walking is more work when wearing these, probably because I shorten my stride to walk heel-toe and have to take more steps to cover the same distance.

p.s. -- If you can find the navy / white rather than the black / white, get the navy!  It looks much better with everything.