For me it beats the 8bitdo by a long shot. I think the 8bitdo only has 2 back buttons, does't it? the vader has 4. And now with Steam input support they are all programmable. I like the feel of mechanical buttons too.
Yeah.. I've been waiting for a steam controller 2 for way too long. The horipad is the only "traditional" controller that has capacitive joysticks.. but beyond having that, the reviews for it are not that great.
Since they are closed source, we can't know. We can find out that messages are being sent at certain moments, but not what data is being contained in the messages, communications carrying this sort of data are always encrypted (for obvious reasons).
For legal reasons they often include some vague allusion in the terms of service about collecting information.. but they are never very clear on what data exactly they take when and how, so it's left up to interpretation.