Yes, I did and it was one of the most wonderful experiences I have ever had. Actually, it was this past June, in Suffield, CT, and the show aired just 3 weeks ago. My volunteering date was on the final day, as the family came home.
My responsibility was truly simple, to bring water to all the workers as the temps were quite hot that day. It had rained most of the week, until that Sunday, and I had been in school teaching, so it was the perfect day for me.
Watching it on TV can not replace the special feeling inside, it was emotionally spectacular!! My late husband and I had watched it for years, and since he had passed only 1 yr before, being there was most amazing.
Enjoy your experience, have your camera ready and feel the warmth of knowing that, however insignificant your contribution might seem to you, you are contributing to the happiness of others.