Of all things new in Lion I feel that this is the singularly uncalled-for feature. What difference does it make to use this 'natural scrolling', other than that one will alienate oneself even further from the conventions of the world?
And there is nothing 'natural' about this method of scrolling. If anything, it is against the intuitive behavior: we interact with the screen indirectly by means of a cursor (regardless of whether a trackpad or a mouse is used), while on the iPad the interaction is tactile and direct on the digital object, thus the necessary difference of scrolling method on a laptop and that on a handheld device. Just imagine scrolling on an iPad as if on a pre-Lion Mac. It just doesn't make sense.
Not everything natural on an iPad is natural on a Mac, and vice versa. I remember Steve Jobs refusing to produce touchscreen Macs on the ground that touchscreen interaction is meant on a horizontal surface of a handheld device, and not on the erect, vertical screen of a laptop. Looks like he backpedalled on his own philosophy.