The night before the Great Balloon Race (http://www.greatforestparkballoonrace.com ) is Balloon Glow. The balloons are all setup close together and as the sun goes down, every few minutes a horn would sound and all the balloons would open up their "burners" and would light up the entire balloon.
We started just as the sun was going down and continued into the dark. I had a tripod all ready to use, but when we got there and I saw the 70 balloons "very close" together and the 150,000 people there I made a quick decision to use a high ISO and shoot handheld so I could move freely among the balloons.
The down side to the 1600 ISO is the high amount of digital "noise" or "graininess" on the images. The upside is I was able to catch shots I wouldn't have had time to compose on the tripod, and didn't have to hassle with always having an unobstructed view..