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.
Yeah the issue is easily replaceable standardized sized battery, if li-ion started doing that, I'd be all in Li-ion band wagon for handheld consumer electronics, till that point I must agree with OP and i would keep demanding Aa batteries and use my niMH cells
Those cells are almost always standard sized prismatic cells, but the connector is often not standard if you buy a random cell.