I'll make the seemingly-obvious argument that is made every time this issue comes up in Internet forums: "natural" scrolling is fine for a single user of a single computer, but if you use multiple computers -- particularly multiple OSes -- "natural" scrolling is anything but natural.
Further, it may be easy to adapt to for one person on one system, but what is the net benefit? It seems to me the sole benefit for "natural" scrolling (and most other Lion changes) is seen primarily in unifying the UI for users who own a Mac and one or more iOS devices. Otherwise, it's yet one more change forcing users to adapt. And yet, the new scrolling method is the default. Was the old way really hindering anyone?
Further, it may be easy to adapt to for one person on one system, but what is the net benefit? It seems to me the sole benefit for "natural" scrolling (and most other Lion changes) is seen primarily in unifying the UI for users who own a Mac and one or more iOS devices. Otherwise, it's yet one more change forcing users to adapt. And yet, the new scrolling method is the default. Was the old way really hindering anyone?