I've been using these things off and on for a while now. My 1.5 mile run time drops a little bit when I'm wearing the KSOs, but that might just happen because the "running" shoes I wear are a really clunky pair of Adidas Bounces.
The novelty wears off kind of quickly, but the five-fingers got me excited about running for a couple months and I haven't stopped running, which is my biggest problem. I live in Scottsdale, Az and the only real problem I have with these things (besides the stares) is that pavement/blacktop road get very hot when the thermometer goes above 95 and you can definitely feel it through the shoe. Its only May, and I'm already feeling a little uncomfortable on the road so I will probably be hanging these up for the summer when we start getting our 100+ degree days.
Probably worth it if you can shell out the $85-90.