Harvard University's Skeletal Biology Lab has an informative site describing the results of their research on comparing the biomechanics of running barefoot (or with a midfoot or forefoot strike) to running with a heel strike as usually done when wearing shoes with a cushioned heel.
Biomechanics of Foot Strikes & Applications to Running Barefoot or in Minimal Footwear
Although they focused on running, their findings equally apply to walking. I don't run, but I walk often. Since I have switched to using Vibram Five Fingers shoes almost exclusively, I have spontaneously transitioned from heel striking to mid/fore foot striking when I walk quickly.
When I started this, I could only walk about 5 minutes at a time on concrete in the Five Fingers. My feet and calves got quite sore from the unaccustomed use. Gradually I have increased the time spent walking. After 3 weeks, I can now walk more than 1 mile with a fore/mid foot strike before my feet get too tired to continue and I revert to a midfoot/heel strike (but still softer than what I would have done before Five Fingers). I also feel the my feet building up new cushions/callouses on the forefoot.
This practice also made me aware that I used my left and right sides quite differently in walking. Some years ago, when I got some Feldenkrais Method "Awareness Through Movement" education sessions with Jeff Haller, he noticed that I spent more time on one foot than the other when walking, but I could not detect it myself -- at least not enough to see it correct. Walking on concrete in Five Fingers made me acutely aware of different stride on my left and right foot -- whereas the right foot contacted softly and the heel made minimal contact with the pavement, the left foot came down harder with less control and the heel jarred against the pavement (after midfoot contact). As I walked along for about five minutes spent just noticing this, it gradually diminished and apparently self-corrected. I've noticed more muscular soreness in the left foot and calf than the right, and had some transient soreness in the left groin not present on the right.
I first learned about this way of walking about six or seven years ago from a book titled Tai Chi Walking: A Low Impact Path to Better Health by the physicist and Tai Ch'i Chuan teacher Robert Chuckrow. Chuckrow describes how to walk "softly" as in Tai Chi, even on concrete, wearing minimal footwear (as recommended by Tai Chi masters). He described how he makes his own moccasins and uses them as his exclusive footwear, and he encourages his readers to make the same footwear. I however continued to wear conventional "walking shoes" and found it difficult to practice the low-impact walking in those thick-soled shoes that have cushioned heels. The shoes virtually forced me to heel strike.
So far I consider this experiment positive. I will keep wearing the Five Fingers as my primary footwear for the foreseeable future. I have in the past three weeks (since starting the experiment) worn my New Balance walking shoes only a couple of times. Before wearing Five Fingers I didn't notice that the New Balance shoes confine the front of my foot and feel uncomfortable, compared to the Five Fingers. Now I prefer the Five Fingers even to my Birkenstocks, which have a pretty wide forefoot bed compared to other shoes. I'll update my report as time passes.