Ok, so I was not a super-early adopter: I waited until July 22nd to buy the latest OS X release from the Mac App Store. (Incidentally, a few hours later I received an email from my university’s IT department saying that we will soon be able to get it for free thanks to a licensing deal with Apple… oh well…).
In a nutshell, so far, so good. First of all, I have yet to find a major compatibility issue, which is great–no downtime. Second, the UI tweaks are cool, including the disappearing space bars (which make a lot of sense: when was the last time you actually used a space bar, given that you can scroll with your touchpad?) Third, I had a hard time understanding exactly how Mission Control was supposed to work when Jobs introduced it, and I was a bit worried about leaving the comfort of Spaces and Expose; but, after using it for less than 24 hours, it’s already growing on me. After all, it’s just Spaces and Expose combined, with support for full-screen apps to boot. By the way, I think the new full-screen mode would be great for LaTeX editing on small screens: you maximize the editing and display surfaces, and have a convenient way to switch back and forth.
Now for the main point of this post. Lion introduces what Apple calls “natural” scrolling. In previous OS X releases up to and including Snow Leopard (as well as on Windows and Linux, on laptops with a decent trackpad), to scroll a page down in your Web browser, word processor, etc., you swipe two fingers down. This may seem natural enough: after all, if you use the scroll bar, you pull the bar down to scroll down, right? But think about this: how do you scroll down on a touchscreen phone (iPhone or Android) or tablet? It’s the other way round: to scroll down, you swipe your fingers up. This makes a lot of sense: if you are reading line-by-line down a long sheet of paper, you want to move the sheet up as you read (think of Hermione Granger reading a scroll in the forbidden section of the Hogwarts library…). Well, this scrolling behavior makes just as much sense on a laptop with a touchpad, and OS X Lion makes it the default. I am quickly getting used to it, because, well, I am already familiar with it: that’s exactly how everything on my Captivate scrolls!
The above discussion was about scrolling a document up or down. But how about left and right? Switching desktops, or to different full-screen apps, also works the “natural” way on Lion: you swipe right to get the desktop (or app) to the left of your current desktop (or app). The animation makes it clear that what you are doing by swiping right is, metaphorically, shifting a very wide sheet of paper where your desktops are “drawn” to the right. The Launchpad app, which is essentially the OS X version of the iOS (and Android) home screen, works the same way.
The question is now, which swiping motion is more natural for moving back and forward in a Web browser? I can see a clear argument for also using “natural” scrolling: think of the pages you visit as if they were drawn on a wide sheet of paper; then, you should swipe right to move the entire sheet right, and hence see the page that was on the left of the current one–that is, the last page you visited before the current one. But, Safari (and indeed Chrome, and Firefox, too, I believe) have long supported the opposite convention: to go back, you swipe left. Why does this make sense? True, the back and forward arrows have always pointed to the left and right respectively (at least, in left-to-right locales). So, maybe the swiping motion is supposed to mimic the direction of the arrow. But, if the back arrow points to the left, doesn’t that mean that you really should think of the last page as being to the left of the current one, so that what you want to do is move the current one to the right to make way for the previous one?
Mission Control is weird in that it supports both metaphors. In the Trackpad preferences, I set “Swipe between pages” to use three fingers, and “Swipe between full-screen apps” to use four; the defaults are two and three fingers respectively, but Chrome won’t recognize two-finger swipes to go back/forward (Safari will). As a result, if I swipe with four fingers in Mission Control, then the metaphor is the “natural” one: I swipe right, and get the desktop to the left of the current one. But, if I swipe with three fingers, it’s the other way round. (Using the default setting, three-finger swipes would give you the “natural” behavior, and two-finger swipes would give you the back/forward behavior).
Anyway, if the above was confusing, don’t worry: you can actually disable “natural” vertical scrolling, and any or all swiping motions for that matter. Still, thinking about these issues highlights the extent to which the iPhone first, and other touchscreen devices later, have changed the way we interact with other computing devices, and still do. Which, after all, was the meaning of the slogan Apple used to announce the OS X Lion release: Back to the Mac.