If you're not using S Voice regularly, you could speed up your home button a little with one easy setting change
Samsung's 'S Voice' assistant app has improved considerably on the Galaxy S4. In fact, it's worth revisiting if you dismissed it on earlier devices due to slow performance or hit-and-miss speech recognition. On the other hand, if you're not using S Voice regularly, there's a quick, easy setting change you can perform to make the home key just a little more responsive.
By default, when you double-tap the home key, you'll launch straight into S Voice. That means when you press home, there's a very short pause while the phone waits for a second button press. To avoid this and have the home key immediately send you back to the home screen, you can disable the S Voice shortcut combo. To do this, load S Voice, then press the menu key and hit "Settings." Next, uncheck "Open via the home key." That's it — with the shortcut combo disabled, the home button should respond immediately as opposed to with a very slight delay.
The same applies to other devices with S Voice loaded out of the box, including the Galaxy Note 2 and Galaxy S3.