Hey I read this post and remembered an article I read in runner's worl on this, after scraambling around a bit to see if I could find the article I remembered they have a website.
It's very interesting read, here's the first paragraph
Cryotherapy ("cold therapy") constricts blood vessels and decreases metabolic activity, which reduces swelling and tissue breakdown. Once the skin is no longer in contact with the cold source, the underlying tissues warm up, causing a return of faster blood flow, which helps return the byproducts of cellular breakdown to the lymph system for efficient recycling by the body. "Ice baths don't only suppress inflammation, but help to flush harmful metabolic debris out of your muscles," says David Terry, M.D., an ultrarunner who has finished both the Western States 100-Mile Endurance Run and the Wasatch Front 100-Mile Endurance Run 10 consecutive times.
Me? I'm not sure I'd ever do it, I live in a humid tropical island that has two seasons, pre-summer and summer, I don't dig the cold and whine like a baby if the heater goes dead.