I have used the Adidas Adizero Boost for 5K to half for the past three years and have been happy with them. They are not like the lighter shoes of years past, but you go with the new technology--the choice now seems paper thin or something between an old flat and a light trainer. I almost wore the Boosts for the marathon last spring but went with the Adizero Boston instead, because the course had long downhill stretches in the first 15 miles.