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.
If it's a popular enough device, Chinese manufacturers will copy its batteries for more than the lifetime of the device itself. I've bought new replacement batteries for a smartphone over 10 years old off AliExpress.
If it's not, chances are it's using one of the standard pouch battery sizes (yes, that's very much a thing, AA is not the only battery standard out there), which Chinese manufacturers will keep producing for longer than the lifetime of the universe.
The only tangible benefit is the hot-swap feature.
To me it doesn't outweigh all the drawbacks of having to charge batteries separately. For a controller like this it literally doesn't matter, you can just plug it in to charge while playing.
For VR controllers it does matter more, but I would still much prefer some explicitly rechargeable standard size, e.g. 14650, with a way for the controller to also be a charger still.
Like I said... This did not change my mind