I've been riding with a midfoot cleat position for a couple of years now. I recommend it, particularly for long distance cycling and long course triathletes. It makes you rely more on your quads and glutes, and less on your calf muscles. Often your calf muscles are what fatigue first during long or hard efforts; moving your cleat toward the midfoot effectively takes that out of the equation. For long course triathletes, this obviously saves your calves during the bike leg so that tey will be more fresh when you get off the bike and start running!
It takes a bit to get used to clipping in differently, but you'll be surprised how quickly you adapt.