Based on the description on their site, the controller includes a built-in battery: "8.39 Wh Li-ion battery, 35+ hours of gameplay… "
That was disappointing for me. Specially condidering the Steam Frame’s controllers make use of AA batteries: “One replaceable AA battery per controller, 40hr battery life”
AA Batteries might not be as convenient to use, but being able to replace them is a great advantage. All my Xbox360 controllers still work fine, but none of my PS3’ Dualshock 3s.
The official docking station could be used to recharge (rechargables) AA batteries so the functionality could remain the same.
People think this is a crazy complaint because the controller has an estimated battery life of something like 30 hours and a wireless charger included. So as long as you remember to put it on the dock when you put the controller down once every couple of days, you shouldn’t have to worry about your battery’s charge.
I agree that being able to hot swap the battery would be nice, but this is closer to having to remember to charge your phone and being able to change the battery in a phone at all is a crazy concept in this day and age.