I've had a couple of Giro helmets, they fit me really well, and one turned what could have been a major concussion into a minor concussion and a busted helmet, so I'm only buying them from now on. I know which one fits me, so whenever I break one I'll just order another exactly the same.
+1 for going into your local shop and trying one on, however. People gave me all kinds of recommendations, but none of them actually fit my head.