The Nike Free running shoe was sold to me with the pitch that they could simulate the ultimate way to run. Bare foot.
This is the way nature intended us to run because all the muscles in the foot, calves and ham-strings are used in the most efficient manner. The feet and legs will strengthen and this in the long term improves speed and helps prevent injury.
The Nike Free trainer simulates this and at the same time protects and cushions the feet of the user. They actually do what they say they can do. I have been using them for about two months and my running times have improved - plus my running posture feels more natural and comfortable. The trainers are super comfortable and lightweight; they feel like they are part of your feet. I have used them on all kinds of terrain - including dirt tracks through woods on a 10k run (my race time 43 min) the trainers handled the terrain no problem.
The only thing i worry about is that Nike will stop the Nike Free line and i wont be able to get anything like this again. I hope they just keep updating the formula for ever.
Highly recommended for all round running, including cross country and road racing; short distance and long distance.