Pretty much what the title says, it would be nice to have a time stamp option in chat. Notice that I said option for those people who don't want to use it. I don't like stuff forced on people when they don't want it.
I find myself answering stuff in guild chat that is old because I'm on another tab or I'm just busy with the game and a time stamp would be nice to help keep track of when something was said.
My concern can be measured in micro-give-a-craps.