After doing some research I have discovered that Curly was the most correct on this thread.
The people that are counting the weight of the shoes along with over all weight are missing a trick. If you you view your feet as the base of a pendulum but consider that the pendulum must be driven forward manually and forced to change direction against the flow of travel it makes sense.
Stick 150 grams on your gut and its nothing but on your feet each gram is 6 times more restrictive than on the upper body.
I am aware of the weight calculation formula for getting faster and I am working on that too but am grateful that I found an old copy of RW that said that the benefits are around 30 seconds for a 10k but the faster the race greater the difference in potential time between ordinary runners and racing shoes.
I think I may have helped you people rather than the other way round, if you all want to knock a minute off your 10k go get some racing shoes