Here are the different signals that the Steam Controller will send for the different buttons, and what you need in your .emulationstation/es_input.cfg for EmulationStation to react to them.
Left D-PAD The left D-PAD will send "hat" signals when you just touch it, and "button" signals when you press hard enough to actually click. Use this for touch-sensitive up/down/left/right:
<input name="up" type="hat" id="0" value="1"/>
<input name="down" type="hat" id="0" value="4"/>
<input name="left" type="hat" id="0" value="8"/>