I wore flip-flops and skate gear in my role in IT for many years. Some of the most brilliant developers I know wore pajamas (because they slept over at work many nights) and Batman t-shirts with cargo shorts to meetings. I fully support creative minds having the freedom to be comfortable. My own company changed their policy a while back and we went from jeans and Linux Ts to Dockers and ties. It shouldn't matter, but I know my creativity dropped after that :)