I'm not a whole shoe person and definitely not a sock person, so finding fashionable, comfortable sandals were like a godsend to me.  My first FitFlops were the bronze Walkstar III sandals, and they were/are the most fabulous, amazing thong sandals I've ever owned.  I absolutely love them.  Once they've formed to my feet (after less than a day of wear) they were/are a dream to wear.  But, then I wanted more colors, so I ordered the silver Walkstar III and a black Oasis FitFlops.  The Black Oasis sandals seem to even fit and wear better than the bronze Walkstar III, but the silver Walkstar III sandals hurt from the get-go and continue to hurt my feet, even after wearing many, many times over last sandal season and into this season--don't know why but somehow they are different, the toe-thong cuts where the others don't and the heel cushion doesn't seem to absorb the shock on heel to toe impact like the other two pairs do.  I now only wear the silver ones when I'm going to be out for a short period of time and never for long walks.  So, whether these shoes work for you could depend on which color you order, or perhaps FitFlops manufacturing process is not of a consistent quality assurance as it definitely should be for the price of the shoes and the proclamations they make.  Although from previous reviews they do have more satisfied customers than non, and perhaps that is the company's acceptable margin of error.  I would still most definitely recommend these shoes, just perhaps if you happen to get a sore pair, don't give up and try another, but that is difficult to expect since one has to wear them for awhile to know whether they will work or not, and current return policies don't allow the return of worn shoes.  Perhaps that is some kind of guarantee/warranty that FitFlops needs to consider if they aren't going to consistently make the same shoe during manufacturing.

As far as fitness--if you've got a properly made pair--for the first time relative sedentary user, one may feel some (very mild) workout burn in their calves and inner knee area to the lower inner thigh  (I did), but that soon goes away after continual wear.  They do seem to help with posture related back problems somewhat.  But these are basically just shoes, so don't expect miracles if you have really bad posture to begin with or any considerable amount of fat to burn off in the legs, thighs, and hips, but whatever walking exercise you take on during the sandal seasons these will help absorb a great deal of shock in your workout and offer a better reach and control than you can get from any other sandal or flip flop.