The Wired test of the Nike Free liked them quite a bit, and they have tested the FiveFingers too. They also don't look like gorilla feet.Of course, I'd wait until your marathon and then recovery.
The USA Triathlon magazine had an interesting strength builder for barefoot running. They suggested that you stand on one foot barefoot as long as you can, up to 30 seconds, so that your toes don't leave the ground (especially your big toe). Then, the other foot. Then, do the same thing with your eyes closed. If you do this several times a day, it mimics the barefoot posture without having to do it all at once or take to the streets.




Of course, I'd wait until your marathon and then recovery. 
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