I use OS X and various GNU/Linux at work and mostly OS X at home as well, but on my personal computers I run Debian GNU/Linux. In OS X, I use VirtualBox and Vagrant a lot to run various operating systems, including Windows, *BSD, GNU/Linux distros and more obscure but interesting operating systems like MINIX 3 and plan9. With Vagrant I can set up such a virtualized environment with a single command as a one-off development server.
OS X is nice though, and I enjoy its BSD user land. It's a legitimate (and certified) UNIX that runs well out of the box as far as I am concerned. Using the different package managers that are available for it makes it very convenient as development workstation.
@TeamBlackFox >> Well the customers I work with uses GUI's since they are regular users.
Maybe your customers are more into consoles, but that can hardly be true for the majority of users.
You can develop GUI applications using a terminal based toolset, you know. In some cases it doesn't matter what the customer prefers, because the customer won't even know that the software is running.