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.
For one, as far as I know that's a single player game. Anyone with other players around means constant slight readjustments, and having everything you do held back (even if only a tenth of a second- I don't know the actual number, that's a ballpark guesstimate) really adds up.
For almost every game it doesn't matter a whole lot. But when it does, it really matters. Bluetooth headphones pad the audio a smidge too, to the point of rather play without sound instead of late audio. It causes constant sending guessing, and if you're using both your leaky playing in a game state that's already past (although when online you always are anyway but cutting as much out as possible is miles better).
Trackmania requires the same precision as other racing games (I also used controller for Forza horizon and motorsport).
Bluetooth audio is a different issue, where my bt speaker adds like 400ms which.. is not suitable for anything where accurate sound matters. Even my bt headset that is meant to be good is uhh.. flawed. But noise is far more obvious than a controller being a tiny bit out.
My controller I can't tell the difference.