I sized down for these -- I'm more often a 40 than a 39, but the 40 was so big! My left foot was slipping in it. The 39 is a perfect fit on my left foot, but very snug on my right (my right foot is bigger). So I was in serious doubt. But in the store they advised to stick with the 39, as they will stretch (the shopgirls were both wearing last season's Dickers). In the length I don't need more space, it's the width that's the problem, and they said that it will stretch to accommodate your foot. Have been wearing them now for 2 days, and they are gently stretching, so I am hoping :-0. But I'm pretty positive the 40s would have been too big for comfort. I don't always want to wear them with thick socks or an innersole. Plus it's really hard to fill up the extra space at the heel.
Hope this will help anybody to make up their minds! A 39.5 would have sold my problem!
I tried - I couldn't get mine to stretch enough - I am sure yours fits better to begin with.