You'll love MBTs!  If you're on your feet all day, you need these shoes.  They take all the pressure off your back and tone your body while you're at it.  Really, the no-back-pain is what I need; the toning is just a nice bonus.

Buy half a size larger than you usually wear.

MBTs take some getting used to.  Wear them for just a few hours a day until you get used to them.