I never used to show my elite cards. I frequently encountered "Sir, this line is for first class or elite paxs only" or after asking about the available room upgrade and amenity "Oh, I didn't know you were a Diamond/Platinum. It's not in your res. Let's see if I can get a better room for you, sir."

Now, I always use my elite card. It's a polite, non-verbal way of communicating my status, eliminates the embarassment of my explaining that I am indeed in the correct line or the need to request published benefits.