I might be in the minority when I say this, but I really cant stand the look of a navy blue suit with black shoes. I dont see it as a flattering look at all, and just reminds me of all the lawyers I see walking around Manhattan in their boxy 2 button suits and black wingtips. I like the look of a nice shiny pair of black oxfords with a grey suit, but I still prefer brown in that situation. Ofcourse black is appropriate and required with a tuxedo (although in those cases I wear black suede), I cannot think of another circumstance when I would chose black shoes. I know the old rule about no brown shoes after six, but to be honest that seems a bit outdated. Considering the level of formality in this country (USA), I doubt I get many consecending stares in my brown shoes while out to dinner. Come to think of it, most men dont even bother changing out of their sneakers anymore, much less worrying about black/brown after six.