Mac OS 10.7 Lion introduced a new feature called natural scrolling that's causing fits for some users upgrading from older versions of the Mac OS X. If you haven't upgraded to Apple's latest cat you can test the new "up is down" scrolling (without installing Lion) by installing a freeware app called Scrollvetica.
But I'll warn you: it's going to drive you nuts.
For years (decades?) we've been trained to drag a scrollbar down, to scroll down a page. Lion reverses this and requires you to scroll or drag up to see the lower portion of a page. It sounds counterintuitive at first, but it actually makes sense, especially when coming from a touch-based device. Lion does away with scroll bars in the Finder, Safari and elsewhere exposing them only while scrolling to provide a visual reference of your location in a particular document.
Because Lion doesn't rely on scroll bars, it doesn't make sense to scroll down to move a page down. Your hand would move down as the content moves up -- exactly backwards with the real world. Lion's natural scrolling is comparable to grabbing a document and pushing (or flicking) it up to see the lower portion of a page - just like you do on the iPad.
Much has be written about the iPadification of the Mac OS and it's now a fact of life that major portions of the iOS (launchpad, full-screen apps, gestures, etc.) have leapt into Lion with both feet. It's time to embrace change and adopt Lion's new scrolling behavior or risk getting left behind, or at least not being able to scroll for a while.
Enter Scrollvetica, which inverts all scrolling events on Snow Leopard, mimicking Lion's new natural scrolling features (and iOS by extension), without installing Lion.
If you spend part of your time living in the future, with default Magic Mouse and Magic Trackpad settings, you may find it difficult to switch between the future and the present and maintain any sort of input device sanity.
I use Lion on my MacBook Air 11 but I have yet to install it on my production MacBook Pro 15 because Verizon's 4G/LTE drivers haven't been updated for Lion (grrr). When I switch between my Macs the whole natural versus reverse scrolling thing drives me nuts.
Sure, I could simply uncheck natural scrolling in Lion, but it feels like I'm just putting off the inevitable.
What do you think of Lion's new natural scrolling? Will you switch?