Yea the hardest thing (IMHO) is zipping the bead all the way around without pinching or destroying the new tube. Hard to do when your hands are shaking and your heart rate is up having just jumped off the bike. practice, practice, practice...
This guy is pretty quick (although I think he "cheats" by stuffing the old tube into his shop apron saving him a few seconds - in a race situation you won't have convenient pockets on the front of your jersey and it's awkward to start with anything in your hands, and it takes time to reach behind you to stuff things back into the pockets on the small of your back... And if you miss, there's another 15 seconds to pick everything up (cursing, ask how I know...)
How to Change a Bike Tire FASTEST- for triathlon, roadies and cyclocross racers - YouTube