Please don't say Linux.
I've migrated my main laptop from Windows 8 to Elementary OS and the only complaint from my very non-technical SO is that things "are different" (i.e. the close button is in upper left corner of the window).
Apart from that, everything just works. In fact it all worked out of the box, with the noticable exception of Skype.
Linux is turning into a pretty viable option. Really.
But really these things are frustrations at first but you will learn the differences and get over them very very quickly. Just ask anyone who switched from win to osx.
1. There was no out of the box support of my particular NVidia video card, so I've had to build the driver from source and fiddle with my system to install it.
2. I've had userspace processes freeze on network activities and become impossible to kill, because of a kernel deadlock in my wireless driver.
3. Proper smooth fonts required work at the time (freetype did not ship with good subpixel hinting).
4. Proprietary media codecs did not work out of the box and required a third-party repositories.
5. The whole KDE four-point-not-really-zero debacle.
A minimalistic XMonad+Vim+terminal setup was decent and worked for me, but eventually I got sick of desktop Linux and moved to OSX.
I realise that many things have been fixed in the meantime, but it was not a flawless experience back then. If I was to give desktop Linux another shot today, I'd be cautiously optimistic, but not expect a miracle.
1. Not an issue anymore in most recent distributions, and Nvidia is now supporting even the latest graphics cards on Linux. 2.3. I can't comment on that. 4. On Ubuntu and many other distros they now work out of the box.
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.
Love Linux, but this bit does disappoint.
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.
But I haven't used Linux in about 6 years, so things might've improved...
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.
-- 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).
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.
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.
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.
Explanation: http://en.opensuse.org/openSUSE:One_Click_Install
Example: http://software.opensuse.org/package/chromium
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.
The fonts appear smudged out and blurry and are much harder to read on normal displays than the anti-aliasing used in both Windows and Linux.
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.
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.