Here is a good slow motion analysis of the motion of heel strike running compared to proper running technique.
http://www.youtube.com/watch?v=XrOgDCZ4GUo&feature=related
My chief complaint with winter in this climate IS the heavier footwear required by the extreme cold. During the snow free months I feel so 'liberated' in comparison and I have discovered neoprene waterproof boots as the ultimate light-weight footwear for use around the farm and garden.
Great running instruction, but doesn't work well for walking.