There are two other problems I thought about later:
1) It's too fast. My Android phone also scrolls like XINPUT2 but it's got a smaller acceleration. But maybe it's what you say about getting used to it.
2) That would work in Firefox and every other window would still scroll in the other way. That's really bad and works against getting used to a specific scrolling behavior. I don't get it: the scrolling behavior should be managed at a level below every application. All the scrollbars should behave in only one way, except the random application that implements its own logic because of some important reason. So I would expect a system wide setting for XINPUT2 or traditional scrolling.
