I had a pair of traintones and wore them religiously for ages. I felt a difference, not anything major, but you can feel the wobble. I stopped wearing them for LBT and Body pump classes as i felt they were putting my knees out of alignment in the squats and lunges and my knees were really feeling it. As a walking gimick i think these types of shoes (MBT/sketchers etc) are good, but not for gym work.
I wouldn't do zumba in them, they won't allow you to twist/turn easily due to the non-slip sole material, they will damage your knees.