It took me about two weeks to feel completely comfortable with the “natural” scrolling system in OS X 10.7 Lion. When I first installed the developer beta, I changed the default setting back to the old way (scroll down, go down). But when Lion was released to the public, and everyone decided to switch, I figured it was a good idea to get on board. After all, if this is what Apple was going to consider normal moving forward, it would be in my best interest not to fight it. It was a tough first week–nearly ten years of muscle memory is hard to overcome, but I eventually got the swing of it. And of course, I immediately installed scroll reversers on every non-Lion machine I used. As any ex-smoker will tell you, quitting only works if you do it the whole way.
I was recently asked why I thought Apple made this change. Was it really the better way to scroll, or did they just decide it should be the better way. I don't know the answer. But I do know there are a lot of people using iPhones and iPads (myself included), and the way we interact with those devices makes a hell of a lot of sense. When you want to see more of a view, you push it up the screen revealing more below. It's intrinsic, much like moving a newspaper vertically in your hand to read a story on the bottom of the page. On a computer with a non-touch display, this way of scrolling isn't quite as logical. Your hands are manipulating an object not directly tied to the screen–the level of disconnect requires some thought. When you rotate your scroll wheel up, which direction should the content move? In the 90s, when scroll wheels first came to market, up was clearly the correct answer. The scroll wheel is an extension of the screen's focus, but it is not the screen or content itself. If you had told someone in 1995 that scrolling up on the wheel would move the content down, they would have thought you were nuts.
Perhaps wheels themselves make this conundrum much trickier. The jump from old-style scrolling to “natural” scrolling felt less painful because I use a Magic Mouse and a Magic Trackpad, both of which are touch-based surfaces without moving scroll parts. When you want to scroll on the Magic Mouse, you swipe on the surface of the mouse. While I'm still not touching the actual screen, the gesture is far closer to synonymous. It doesn't take much of a logic leap to imagine my fingers are swiping the screen itself, which makes the “natural” scrolling feel exactly like it does on iOS.
Long-term, I think Apple made the right decision. As all television and movies have shown us, in the future, at some point, our computers will use a combination of voice control and touch, and not a lot of mice. Have you ever seen a sci-fi show or movie that takes place more than 10 years from the present where people are using computer mice? It's ridiculous. Moving a cursor around the screen with a small chunk of plastic made sense in 1984, but the closer we get to 2020, the less necessary it feels for average people–just look at how many people use an iPad as their primary machine.
If you will, allow me a few final thoughts on the subject:
There are a few strange things that come from using “natural” scrolling on the Mac, and most are related to applications that assume scrolling directions go the old way. The biggest issue I face on a regular basis in in Google Maps, where scrolling up zooms in and down zooms out. Only with “natural” scrolling enabled, the actions are backward. If you flick up on your Magic Mouse, Maps will zoom out. For some reason, my brain wants this to work the opposite. But if you abstract what's happening, it actually makes more sense–flicking up (toward the screen) pushes the map back (zooms out) and flicking down (toward you) pulls the map in (zooms in). Or at least in theory this makes sense. But I've been trying to tell my brain for months and it still doesn't take. I always start by accidentally zooming out and then zooming in.
And what about the scrollbars? Lion hides them by default, but when they appear, they feel backward to me. I flick up on my mouse to scroll down, but when I grab a scroll bar, I need to move it down to scroll down. If we're going to change scrolling to act like iOS, where we assume our scrolling is the equivalent of grabbing the content view and pulling it up the screen, then why on earth do the scrollbars act the exact opposite? Shouldn't actually grabbing the view, by clicking on it and holding it, work the same way as swiping? I would expect to grab the scrollbar and drag it up to scroll down, just as I use my finger on iOS to drag the view. Perhaps instead of thinking of the scrollbar as a scrubber, we should think of it as a scroll indicator (much like on iOS), and the entire invisible scroll track area as a space in which the user can use the mouse to directly grab and move the view. This way, you can move your mouse to the right 2% of the view, click and hold, and pull that view around much like in iOS. Want to scroll down with the mouse? Move it over there, drag up in that space. This feels like it would make a hell of a lot more sense to me, but when I tried to explain this all to my dry cleaner he seemed pretty nonplussed.