It's all quite simple, really. The Samsung Galaxy S III can be set to open up S Voice with a double press of the home button. The only problem with that is that after the first press of the button, there is a pause as the phone stops to see if you want to go to the home page or open S Voice. It's the same thing that happens anytime a handset manufacturer decides to offer double-tap functionality to a button. So if you want the ability to get to your home page more quickly, you can go into the settings to disable the double-tap feature.
Had Dorothy been toting a Samsung Galaxy S III when she ended up in OZ, she might have only had to click her heels once to get home.