Is there a reward for earning all of the gold medals in time attack mode?

After completing world 1, Jungle, I went back to find all the puzzle pieces and K•O•N•G letters, and earn a time-attack medal in all the levels. When I found all puzzle pieces and letters in world 1, but before I earned time-attack medals on every level, the hidden 1-K Platform Panic level unlocked/appeared.

This leads me to believe that you don't get anything for earning any time-attack medals.

I don't think there is anything to unlock after you get them. Like Chad said: "Only ulcers and high blood pressure".

Did you know there is a Shiny Gold Medal? You get that if you finish in the fastest time possible! And I thought just getting the plain old gold medal was hard… I even asked a Nintendo Representative and all he told me is "Just keep playing and see for yourself." I hope it has a payoff in the end after all that hard work. And I know you have to be lucky to be able to land a hit on some of the bosses, which makes it hard.