I always had the same reaction to those as I did to the socks that were a fad when I was a teenager.
Isn't it uncomfortable to have material between your toes? It's one thing for flip flops, but the thought of having a seam and cloth between my other toes just makes my toes feel itchy thinking about it.
I keep meaning to get a pair of those minimalist running shoes. Not for running, but they look comfy. But I don't want the finger toe thingys. I honestly can't imagine running in them. It's one thing to land on a rock or other odd spot on the ground in light soled footwear when you're walking, but running? Owchyyy!