This is another great post I found that reviews the issue of transitioning to midfoot strike.  It emphasizes several points.  The first again is that midfoot and forefoot runners generally run faster.  The second which is just as important.  If you are making the transition from a heal striker do it gradually.  Those people that changed quickly to a barefoot or even a Pose method broke down with Achilles injuries.

From the article

And with the advent of Pose and other running techniques, as well as the observation that not all elite runners are landing on the heel first, people have now begun to advocate that forefoot landing is better! So we have this 180 degree shift, often in the absence of any substantial data to support the claim.I am sure that many will have seen this kind of assertion (this one is from Wikipedia):Leaning forward places a runner’s centre of mass on the front part of the foot, which avoids landing on the heel and facilitates the use of the spring mechanism of the foot. In other words, landing on the heel is bad, to be avoided…Or there is this, from Gordon Pirie (admittedly somewhat older):Running equals springing through the air, landing elastically on the forefoot with a flexed knee…But what is “better”? Where science has yet to catch up with opinionIt’s important at this point to ask the very pertinent, but infrequently asked question: “What does ‘better’ mean?”. In other words, when people are advocating that it’s ‘better’ to land on the forefoot, what do they mean? Is it faster? More efficient? Less injury-prone? The fact is, the word “better” is used without studies specifically looking at any single one of these aspects. And the ‘prudence concept’, as applied to science, says that you cannot say something is “better” unless it’s been studied and compared to the alternatives. Unfortunately, the science lags behind in this regard.So for example, above you have the quote that you are supposed to land elastically on the forefoot. That implies performance and efficiency, which might be true for short exercise, lasting a minute or two. But in an event like the marathon, are we sure it remains the “better” option? If you went out and ran 2 hours today, landing on your forefoot instead of landing as you’ve always done, what would be the likely outcome? Chances are, you’d be hurting for a few days, with calf muscles that you had perhaps forgotten you had! Worst case scenario, you’d be injured for months with an Achilles tendon injury. That is certainly not a desirable outcome. So there are problems with making sweeping statements about landing patterns.But more than this, these kinds of statements are never grounded in proof. So for example, when it’s written that you land “elastically”, has anyone ever done the study of elastic energy return in different types of running? They haven’t, but there is theory about it, and that’s where these recommendations come from. So the approach in the discussion that follows is for me to adopt the role of “questioner”, playing Devil’s Advocate, with the humble admission that science simply does not know the right answer, only the possibilities…Looking at one particular study – elite 21 km runnersSo in the current climate where real evidence is scarce and opinions hold sway, let’s take a look at one study that has examined footstrike patterns during running events. It was done in 2004 in Japan, and published in 2007 in the Journal of Strength of Conditioning (not sure of the reason for the delay – it happens sometimes in science!). The full reference, for those interested, is Hasegawa et al., J Strength & Cond., 2007, (21), 888-893It was performed at the 2004 Sapporro International Half Marathon in Jap

Source: Running technique: The Footstrike | The Science of Sport