I'm curious about this as well.
I got a good deal on Adipowers as my first weightlifting shoe and I'm trying to figure out if they fit properly. I bought them 0.5 sizes down from my regular shoe size. I can't really go smaller in length as the toes of my larger left foot are at the end of the toe box.
When I have them on and laced up, they feel snug, but I can definitely wiggle my toes and twist my foot a little lengthwise along the axis of my foot. I don't feel danger of my heel lifting, but I don't want there to be too much room.
I'm wondering if my opinion of their fit is skewed from my experience playing soccer and rugby and wearing cleats that are really tight.