A couple of years ago I was traveling from TUS to IAH on a Continental coach reward ticket, and I had neglected to get a seat preassigned. At check-in only middle seats were available. I asked if there was any chance of getting a "Better" seat at the gate and mentioned that I was a Gold Elite "If that made any difference" The gate agent told me to wait a few minutes, and then gave me a FC boarding pass! A similar event happened when I was traveling from MCO to DEN with my wife, who was traveling on a reward ticket, I was on a discounted coach ticket.
The flight was overbooked in coach so I was able to persuade them to upgrade us. (I was Silver Elite at the time)