I wear the Vivo Barefoot Oaks http://www.terraplana.com/oak-p-2165.html?colour=143
every day at work, they're leather, and no one really notices them as being out of the ordinary. 4mm thick flat sole.
I will likely get some Sanuks for more casual wear in my next shoes.
Just had to fix my Vibrams with Shoe Goo, they were coming apart in places.