I have one. A gold 14t. I got it used. I don't notice any difference. It's just my bling race cog that I would leave on the disc.
For color coding, I once bought a set of paint pens and painted the face my 13, 14, and 15t cogs cogs a different color. It helps when you are grabbing one out of the track sack or when you look down at the wheel on the bike and know what cog is on. There probably isn't enough face to paint on the 12t though.
Oh...and I bought something, too:
