I used at OS X at work for 2 years and hated it. It's a nightmare for doing real software development on. Now I have a GNU/Linux workstation and things are much better.
I use OSX every day for "real development". I develop in Java and I can deploy the same things from OSX to my Linux (Centos) servers and know they're going to work as expected. In addition to similar environments, I can use real MS Office so that I can actually communicate with the rest of the corporation and have exactly the same formats and such (which is a huge time saver on both ends).
It's clear that OP, just like you, are not in the market for OS X (I am not even talking about windows, or probably ant proprietary OS).
For me, OS X is the best option, I do not need to deal with Linux intricate setup, but I can develop software I want to develop. OS X, in my case, is developer friendly, just enough so I can do what I want, and casually friendly enough so I do not need to worry about some (broken) things, I do not want to be in my way (FileVault, Time Machine, printing[1] and any other nice feature for everyday normal guy[2] (mail/picture/pdf annotation, continuity, Photo/Video editors)).
I want to stress, that I know that many equivalent software and features exist in Linux world, though usually it is much more troublesome to use. Not everyone is (or want to be) Linux guru, rockstar hacker or simply willing to solve bugs or errors for and at uncertain time.
Simply, Linux vs OS X is a flame war without any point. Everyone has a subjective opinion and discussion must end there.
It's a nightmare for doing real software development on.
For you. I have programmed C, C++, Prolog, Java, Go, and Haskell on OS X since 2007 without any problems. If you go to any developer conference, you'll see that a sizeable chunk of the audience agrees.
Cue the OS X apologists.