Often you'll read that "you need your body to get used to them" what absolute rubbish, if your body needs to get used to something then it's obviously something that goes the natural way your body works.
As i say i own a pair of 5fingers and i've given them time for my body to get used to them and without a doubt my body is noticeably sorer after a hike wearing them.
In my opinion it's just a fad and a fashion that's going to be forgotten in a few years.
Sure some mega light weight runners that run very light on their feet might be able to "get away" with them, but that doesn't mean that the 14 stone bloke down the road is going to be that sake does it.
If you can get a pair cheap i'd say try them, at least you know yourself then.
But from my experience it's just another fad with followers that are bordering on fanatical which to honest tends to put me off before i start.
I'm not fanatical, or for that matter much of a runner, but I've using what is now called minimalist footwear for quite a while for most things, and going barefoot as well.
Got a pair of vibram Five fingers KSO last year, I've used them down the gym, around the woods and skateboarding (middle age skater), and TBH I prefer going barefoot.
It may be a fad but there is some truth behind the myths, however you definitely need to give it time to get your body accustomed to it.
Odd thing was I've often worn flat soled shoes, but when I started running I believed the hype and bought some all singing and dancing running shoes, which completely trashed my ankles, same thing happened when I bought some high end walking boots with "ankle support" and anatomical footbeds
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In Conclusion-- Not for everyone, but try it you might like it.
BTW I'm around 18st so definitely not a lightweight.