I've been wearing these shoes for three weeks now, and they're quickly becoming my favorite work shoes. I'm on my feet for 10 hours at work and I needed something with enough cushion and support, but that looked decent too.  I've had my share of Frankenstein nursing shoes!  These are great - they look sporty, the color combinations are cute, AND they're comfortable to wear for hours.
The first two days I wore them, I bounced everywhere I walked.  I felt like I could never place my feet solidly on the floor, always either forward or back.  Once I got used to the rocking motion, I was able to adjust my gait.  I'm not sure they'll really help tone anything, but the comfort alone is worth it.
As several other reviewers have mentioned, the sizing ran small in my case.  I normally wear an 8.5, and these shoes in a 9.5 are the perfect fit.