Update: Motion Controls
One of the more understated features with the Steam controller is the addition of a gyroscope for motion control. While it can be used to simulate an analog stick or even individual buttons, when I tried using motion control to play Sonic and All-Stars Racing Transformed,* I quickly went back to just using an analog stick as it was just simpler.
Where the gyroscope really shines is when controlling the mouse. I found that playing around with the gyroscope sensitivity options gave me several different options for playing FPS, for instance. I could crank the sensitivity up and wander around with just turning my controller left and right, which worked surprisingly well but probably still not the best way to play, or I could keep the sensitivity low and use it to fine tune my aim. In addition, Valve have kept a huge amount of customization for this area as well, and one of the coolest options is making motion control only activate when youre pressing a certain button or have your thumb on one of the trackpads, which does wonders for making the motion control feel manageable.
And at the end of the day, you can always just ignore it. But I recommend at least trying it out.