MBT shoes

Has anyone used these? Massai Barefoot Technology. They look crap, as if half a melon is strapped to the underside of your shoe, and cost a lot - around 100 quid. But...if they do as they claim, and create an instability that makes you strengthen the core muscles, ankles etc as you go about your daily business, then maybe they are worth a shot. The website even boasts research (very small sample) supporting a claim to improve lower back pain, which would suit me just fine. I'd like to hear some reports before shelling out such a lot on an ugly shoe!