Well, for people who were using another OS not especially great for dev-work (there's nothing special about OS X in that regard) it seems like a fine recommenda

Well, for people who were using another OS not especially great for dev-work (there's nothing special about OS X in that regard) it seems like a fine recommendation. The biggest reason to run OS X apart from the obvious "you should do it because you want to develop for Apple stuff" is that it's a clean experience that mostly gets out of your way and you won't have to tinker all that much. The macbooks are well tailored for dev work because the hardware itself hits most of the points that people want and care about. There are arguably more options for dev work on any linux distro and Arch, for example, will do a better job with its repositories and the AUR in giving you easy access to devtools (and all other apps) of all kinds.