It depends on the outfit, in my opinion. If all (brown shaded) leather items match each other perfectly, it can scream OCD or trying too hard in casual fits such as the one Dropbear posted. Also applies to matching metals.
However, it can also give a more streamlined and polished look when done in a more formal/business casual context.
I would always prefer different shades or textures. Some shoemakers offer belts in the same leather as the shoes: never an option for me.