10 years later and pretty much every distro works out of the box on pretty much all hardware, but back then Ubuntu was definitely ahead of the pack in these regards.
I do appreciate the strides Linux has made since a decade ago, but I still think that's crazy talk. I've never seen laptop hardware that Linux "works out of the box" on, and I've installed it on at least 15 laptops in those ten years.
I mean if "works" is defined to mean something equivalent to what macOS or Windows do. Wi-Fi, webcam, bluetooth, graphics acceleration, highres screen, sound, fingerprint reader, keyboard backlight, hardware volume/brightness controls, multitouch trackpad... at least some of those things are always broken on any mainstream distro I've tried, including Ubuntu.
Doesn't mean Linux isn't awesome, but saying it works out of the box on almost all hardware is a pretty radical downward redefinition of "works".
Buy any > 2 year old Dell Latitiude and it will work out of the box. Maybe the (IMHO useless) fingerprint reader not, but all other stuff will work. Had at least 5 different models.
Also highres screen is an issue which is not fixable because you need to fix every software. Same applies to Windows in this case but it does a better job in pixel scaling non-HiDPI apps (but they are still ugly as hell in many cases).
I've recently bought a HP ProBook (a xx75 model) for dual booting of Linux and Windows 7. Imagine my surprise when in Linux everything was working out of the box, whereas in Windows I had to actually use another laptop first in order to load WiFi drivers. Even USB 3.0 ports didn't work under Windows out of the box.
Look for almost any Dell these days. I've used 6 (Vostros, Latitudes, Precisions) in the last couple years and all worked flawlessly from the start (except for the fact I had to uninstall Windows in all but one Vostro). I also use Linux on a small and light Acer "Cloudbook" (a Chromebook-like that comes with Windows). This last one was a bit confusing to install because of the UEFI/eMMC combo, but after understanding the peculiars of the installation, it worked perfectly ever since.
And it was Ubuntu 16.10, because that's what I found on some USB stick lying around and was good enough.
From my personal experience, my Lenovo Yoga 2 Pro is almost 100% supported - the only thing that's not right is the detection of various keyboard orientation modes (tent mode, presentation mode, tablet mode), so the keyboard and touchpad isn't reliably disabled when it should and the UI isn't notified about laptop/tablet mode switch. Looking forward to 4.16, which apparently carries some fixes in this field.
However, while it worked correctly on the Windows installation which came together with the laptop (until I've removed it an hour later :P), some time later I had to install Windows for a moment, so using the chance I wanted to install all the OEM drivers to see how it works there (of course, out-of-the-box it didn't work at all ;)) but... I couldn't. Seems it's only supported by the installation prepared by the manufacturer (and by its recovery partition), nothing else. Even the automatic screen rotation didn't work - a thing that works reliably on Linux.
While probably "all hardware" is a big stretch, from my experience there's is a big chance that everything actually will work out of the box and it's definitely way better than it was 10 years ago, when for instance I had to install OSS4 and get all apps to play nice with it just to get the sound card on my desktop supported :P
Even my Eee PC 1215B, which was sold with Linux pre-installed, had wlan driver issues.
And nowadays with the whole AMD driver split, the 3D acceleration went down. For example, now I have to force enable it on Firefox.
Ubuntu was noticeably faster and more stable so I chose Ubuntu. It turns out that what I was really seeing was Ubuntu was faster and more stable in Virtualbox and since that is the only way I can get Linux on my work desktop this is important to me.
I'm sure many people use Linux this way, so this will continue to be important.
Maybe Debian would be OK now, but Gnome 3 takes up far too much of the screen on my laptop with menu bars, and this is why I am sticking with Unity for now