I think wearing sunglasses while playing poker is cheating. The art of the game is not only in how to play the cards, but also how to read other player's without giving away your own emotions. Wearing a low ball cap, a cowboy hat or sunglasses to mask your facial expressions is a cop out. And I wish more professional players would take a stand against the use of "disguise". It's like giving a baseball player a larger glove.
Just my two cents.