I have been wearing my new Sidi Genius 6.6 Carbon Lite's for a couple months. I love this cycling shoe for several reasons. They are light, stiff, and adjustable in ways other shoes are not. I wasn't sure about the heal cup adjustment at first but it keeps my feet securely in the shoe. No movement at all in the heal. The velcro security straps are VERY secure. It was easy at first to over tighten them and cut off the blood circulation to my feet. They do not give once tighten, unlike my older Sidi Genius 5 shoes. I wear size 41 which shows as US 8.75. My older Genius 5 are size 41 and slightly tight. The Genius 6.6 Carbon 41 is perfect and feels a tiny, tiny bit longer which I like. My normal street shoe size is 8.5-9 depending on the brand.
You can not go wrong with these shoes.