Though I often have a beard during fall, I learned many years ago that it's important to cover as many contrasting body parts as possible, especially those that move alot...namely the face (mask) and hands (gloves). It's also a good idea to practice frequently with these items. In fact, I wear a light jersey glove under my tab all year (backyard summer practice, 3d shoots, etc.), to ensure that I stay used to the 'feel' of a gloved release hand. A fletch cover for bright arrow fletching is also a good idea.
Deer don't survive in the wild by being stupid and anything that 'flags' their eyes is obviously bad for the flagger. For the close shooting that comes with bowhunting it just makes sense to blend in as much as possible.