Wait, fucking BATTERIES in 2015? I'm out. My hype was in outer space and now it's buried. Fuck you Valve.
After using a wireless 360 controller and ds4, i take the rechargeable battery option any day. Instead of messing with charging wires, bad battery life or using second identical controller, i can just throw in charged batteries every couple weeks.
Also it looks like there could be option for battery pack, charger or similar in steam controller.