* It's powerful enough for my development work.
* It's small/light enough to take with me.
* For my work the battery goes for 14 hours.
* It's not so expensive as "premium" laptops go.
* OSX with homebrew has all the things I like about Linux, but wifi and power management work flawlessly out of the box.
The batteries on those machines are amazing. They really last for 7-9 hours depending on use. The 2013 one is starting to show the "Service battery" warning every now and then but no performance degradation is noticeable yet. It's been through 380 cycles so far.
If you use a non-Retina Macbook like those, I suggest using a bitmap font for programming (I'm using Terminus myself). It's totally sharp and easy on the eyes. Crank up the contrast in your editor's color theme and you're all set.
That said, I've been keeping an eye out for alternatives for future replacements after my current Air dies, as Apple seems to be flirting with ending the line? Or it least it seems like a stepchild wedged between the Macbook and Macbook Pro lines. A premium build, portable laptop that runs well integrated Linux would be nice - but honestly I'm skeptical that a competitor will emerge. Maybe a librem 13.
I'm considering getting a new machine in the coming year, but also don't feel like its critical that I do it.
Plenty of go for web browsing, compiling embedded code, and LaTeX, so long as you don't need to run 20 virtual machines, do video encoding, or play games.