Whenever i fly in First Class I wear a nice shirt pants and shoes. I feel that it represents who you are and it shows respect. If its an overnight flight then I would wear a nice polo shirt and a pressed pair of jeans or chinos. I consider flying in First Class like going to a business conference.
Respect for what? Unless you're a nonrev, travelling in F isn't a privilege, it's a right paid for with a large sum of money/miles.
Aren't you the famous danielonn who thought you were going to get the VIP red carpet treatment because you were flying on your birthday?