I have been wearing them for 4 years and love them. Prior to that I got kitted out with cushioned shoes ..went on the treadmill and everything to get the right type and kept getting knee issues. I have had no more knee issues since wearing the vibrams.
You do have to have patience though..to build up but I have always been good and not pushing it too much and easing off when I need to. I run a lot and I just absolutely love how grounded I feel in these.
Personally though, if I hadn't have had knee problems and wasn't trying to resolve that I would have never tried them. It seems in the last 4 years though they have become much more expensive and there are lots of different styles of minimal shoe now that you could use.
I think even if you have no injury problems you may get a lot out of using them but you have to have patience...and I suppose I don't see the point of changing shoes if you are running fine in what you have.