Photographing fireworks is always such a matter of trial and error, and mostly error. You don't get a second shot, unless you have a second firework to set off! Exposure, especially, is a guessing game: too much, and your image is blown out with nothing but white spots; too little, and your image loses its spark, so to speak, disappearing into the night. And then there's the matter of proper timing, especially when something blows up.
I was extremely pleased with the way this image turned out. The exposure and timing are perfect; you can almost hear it go "bang" in the night.