This. I switched to OS X from Ubuntu about a few months ago simply because of this reason. I was too tired of tinkering and configuring endless .conf files, adjusting my GNOME/Xfce panel layouts for optimum productivity, and changing my display manager because all of them sucked.
In my final days with Linux I was running Ubuntu Minimal with twm -- I went completely old-school. Fewer things at the core, fewer things to go wrong.
I caved and bought a MacBook Air. While I miss the endless configurability of Linux, I find that most of the time I spend trying to configure OS X is only spent to make things more suitable for my workflow -- changing the number of desktops I have, changing the applications in my dock, or adjusting Exposé to show all app windows.
I never have to configure something because it breaks or isn't compatible with something else. I could have gone the FreeBSD way, but then, well, you know. OS X just works. As a Ruby and Java developer I find it perfect. I probably will try the 13.04 release on the Mac (I tried the beta and liked it), and I'll see how it goes.
It looks like a solid release, so I'd really like to keep it (but I probably won't because I'm cheap and only have the 120gig SSD).
But I don't spend days tweaking the UI, I have a baseline of UI expectations that's not too difficult to meet. (But Windows 8 doesn't meet it... 'nother story for 'nother day...)
Something is wrong here. The massive shift of devs from linux to OSX should warn some people somewhere about the overall quality of their stuff. A quality that we have been proud for decades.
As a Mac user that runs triple boot, the "just works" mentality in OS X is present only as long as you don't step out of the typical use case scenarios. It's great to say be a writer on OS X; there are very good tools and apps to write in a minimal, esthetic environment (WriteRoom and others). On the other hand, as a "hacker", I've always had trouble in OS X -- from Page Up/Page Down not registering properly in Terminal, to full NTFS and EXT4 support (FUSE used to work, but I think it was not maintained) to getting vim, gcc and other tools of the trade working on OS X (yes, there are ports-like systems on OS X, but hardly ones that I'd say "just work").
On the other hand, in pure Linux world, brightness controls, backlighting controls, volume controls and multiple sound card support were all rather tricky when I tried using Gentoo on the same Mac for a time. Some of those I solved, but some I just gave up and was content that it kinda-but-not-completely works.
Ubuntu seems to be tested enough on Macs, so those things work on my laptop now without having to configure too much. It may not be the perfect "just works" experience, and I have seen a lot of things going the wrong way on Ubuntu, but currently it's a good mix of being easy to maintain and being easy to start doing actual work with.
There's a huge QA process for Ubuntu now -- packages have to go through a large swath of automated tests, and the alpha/beta versions are kept working on a daily basis. It was only 2 years ago or so that most Ubuntu developers didn't even expect the unstable release to be usable until the feature freeze milestone had well passed.