I've been using my Bikila's for a month now - 4 runs a week. I love them! Yes, there's the initial getting used to, with calf-soreness and some strange looks from passersby, but otherwise, it's helped my form and has been a fun reason to run!
I agree with another poster that at first the material was tight on the top of the foot, but that never actually bothered me when I started running, and now has stretched to the point that there's no tightness (not to say it's stretched out, just that it's formed to me now). I have gotten no blisters or heel chafing, but I would say that sizing is so important. So if you buy online, you still might want to go to the store to make sure you've got the right size. Based on measuring my feet, I was a 39, but after going to the store, I realized I needed a 38, which fit me perfectly.
Best part of my run, bar none: running through the wet grass or feeling a breeze all the way to my toes in the Bikilas!