A guy here who went to the states once did a demonstration of this using one of my heifers- it's quick and easy, but as has already been mentioned, you need to do it a fair while before the show because the singed ends are quite hard to get out. Also, on white cattle the hair can go yellow further than just the ends.
It's a good idea if you've gotta do 30 or 40 head quickly, but in the long run clipping is the way to go, imo.