Chinese language fonts (especially when mixed with English fonts) and input methods. And I don't just mean the default fonts the OS comes with (those these are better on OSX by a wide margin), but the way font selection and fallback works for GUI elements that contain a mix of Chinese/English.
I've run both linux and OS X as my default setups (currently linux), and I have to say, OS X does a lot of things better. I like linux better overall, but that's just too strong a statement. Here's a few that OS X does better:
-- Font anti-aliasing.
-- Package management - people using linux should be expected to be able to compile from source, I know, but at least most packages released for Mac OS X are developed with binaries.
-- Graphics card drivers, specifically Nvidia (which Mac ships with).
I've been using Linux and BSD for thirteen years and I can't even remember the last time I had to manually build and install an application from source (not counting random, early-stage hobby projects from github and things).
Open source Unix systems are the kings of package management. OS X pretty much does the exact opposite of 'package management', and any third party solution is based on existing Linux and BSD implementations.
Replying to this because I can't reply to the child comment.
This is something I keep hearing, and I keep linking to the same thing. "Download and One-Click Install" can easily be done on Linux. In fact, that's even what it is called: "One Click Install", at least as far as openSUSE is concerned.
Bonus: It still adds a repository so you have a working update path that plays nicely with the centralised package management that lets you manage every single package centrally, instead of having half a gazillion individual updaters, bundled libs etc.
"Package management" is the wrong term. OS X just makes installing software less terrifying.
Let's say you wanted to install Google Chrome. On OS X, you go to chrome.com and click the single "Download now" button, and it downloads.
On Linux, you get the same button, except clicking it takes you to another screen where you have to know whether you are a "Debian/Ubuntu" or a "Fedora/openSUSE" user or need a "community supported" version, and whether you want the 32 bit or 64 bit version, and whether you want to "add the Google repository to your system", and here's a thing to run on the command line if you don't want that.
The "sudo apt-get install yadayada" stuff is legitimately great for power users. But for most consumers, the OS X approach is definitely to be preferred.
OSX works out of the box because the hardware is known in advance.
If the hardware is supported by Linux, today's distros work out of the box too, and Linux supports a lot of different hardware components, especially older ones.
If you buy a new machine which comes with Linux pre-installed, like OSX is preinstalled on Macs, you can be pretty sure that it works just as "out of the box" as OSX does.
My experience is that when a UI feature is present in OS X and Linux, the OS X version will typically (though not always) be less buggy and more polished.
I've got Ubuntu 12 open in VMWare, running Firefox, and so I can compare it to my Mac running Mountain Lion. I'll pick on window resizing. Here are ways that Ubuntu's window resizing is objectively worse than OS X:
1. The resize edges on the right, left, and bottom are exactly one pixel in extent. They're nearly impossible to hit.
2. When resizing the Firefox window larger on the left/top sides, there's ugly flicker and transient drawing artifacts on the right/bottom side.
3. The resize cursors are misleading. For example, if I grab the top and resize the window as tall as it will go, the cursor still implies it can grow taller. On OS X the cursor changes when the window reaches a limit.
4. An Ubuntu Firefox window can be sized down to three pixels wide. It's hard to click on this window to make it bigger again.
5. Ubuntu allows me to position the window under the launcher and then resize it smaller. Such a window then gets "stuck" behind the launcher. I was also able to get an OS X window stuck behind the Dock, but it was harder: I had to make the Dock smaller, reposition the window, then make the Dock larger again.
6. If you position a window partially offscreen and then try to resize it smaller, it does this weird jitter thing.
7. Ubuntu does not appear to support background, fixed aspect ratio, or centered resizing, which are power-user features in OS X that you can access with modifier keys. If I hold down the shift key, then the Ubuntu window does some sort of snapping thing where it alternates between being as wide as it can, and being three pixels wide (??)
That's from a few minutes of poking around with a single UI interaction.
This isn't a fanboi post. While I like OS X, I noticed things that Ubuntu does better. But in turn, an objective Linux user cannot miss the many things that OS X does better.
I don't know the current state of high density display support in X11 (and I may just be an ignorant user and plain old wrong about this), but it was a totally broken deal breaker for me a year ago.
Cater to naive users. I say this as someone who particularly dislikes Apple's way of doing things, but who still recommends OSX to naive users.
Something goes wrong with linux? Better hope there's a congenial neckbeard around, and if it's a hardware problem, good luck to you. In OSX? A larger online presence, and then of course you can always take it into a "genius" bar... and they replace the hardware gratis often enough.
IME, Linux has a long way to go for non-dual-head setups. I have four monitors with different geometries on two graphics cards on a Hackintosh and OS X handles it seamlessly. Ubuntu pukes hard and dies (or, almost as bad, just ignores monitors) when it can't figure out how it should handle them all in a single X session.
A single X session cannot span two graphics cards. X just doesn't support it. You're waiting on Mir or Wayland for that one.
If you manage to get all four monitors on one card somehow, X can handle the multiple geometries just fine. Though it will generally do a terrible job of automatically detecting the right resolution.
In my experience the state of graphics drivers is still a bit of a sad affair on Linux in general. I never got my two screen setup working properly, not out of the box, and not after fiddling with xorg.conf etc. for more than two days.
Also switching the system language on the fly.