i am seriously considering this (5/30/15)
I read another article where the writer proposed that this is the practice of many successful people, including Steve Jobs, Michael Kors, and Mark Zuckerberg (and I would add Fran Liebowitz to the list). They wear what they're most comfortable in and that makes them confident. It also makes them distinctive, which is good for personal branding.
I don't have a lot of clothes - or shoes - and I have a monochromatic, linear style. There are probably 2-3 outfits I like so much I wish I could wear them everyday. I spend an inordinate amount of time trying to pass those few outfits off as something different, or to try to find a new combination that camouflages my weight gain as well as my go to's. It would take a huge load off my mind to have a work "uniform".