Been lurking for a while, figured I'd register and contribute a little bit.
I recently switched to VFFs on a bit of a whim. Little back story: I had been running in a pair of Brooks Trance 9s on the recommendation of a running store in my area, and they were nothing but trouble. I ended up on crutches with pretty serious pain in my right foot, ankle and heel. I was just running, and the pain shot up my heel, didn't step on anything, didn't twist my ankle, nothing... my foot hit the ground, and then I did. X-rays were negative, Achilles was intact, docs couldn't find anything seriously damaged, so they recommended rest, crutches, and ice. Considering my prior experience with crutches involved me falling off my porch when I was a kid, I wasn't stoked. Months and months later, I started running again with my gf, and at the end of a run I had similar pain in my left ankle/foot, only not as severe. Since then, my runs in those shoes have always involved some sort of pain/discomfort while out, it was just a matter of how severe... Aside from that, I was beginning to have problems with a pair of my casual shoes. One day after a long day on my feet playing shows (moonlight as a musician), I could hardly walk due to pain in my right foot.
I had begun seeing things suggesting that my shoes were likely the crux of the issue, so my GF grabbed a pair of Bikilas for me. After adjusting sizes (she got them while I was out of town, needed to go a size up), and giving myself a week to get accustom to them, I went out for my first run, and was super stoked that I had NO pain during, or after the run... aside from sore feet. Unfortunately, my zeal meant I pushed too hard, too soon, and developed tendonitis in my feet. So again, I was gimping around for a little bit.
I'm just about healed, so it's time to start up again... this time making sure I take it slow.
Another note, since I switched to wearing VFFs almost full time (I don't wear them to work, except on casual Friday), I've noticed a slew of issues have gone away, most notable being the pain and stiffness in my right knee. I usually favor my right leg because it constantly bothers me, but since I've switched, the stiffness has subsided. It's not TOTALLY gone, but it's much much much less profound, to the point where I no longer favor my leg, and it doesn't bother me, even after a long day of standing up.