If memory serves me well, the appeal of OS X to unix pros became a selling point quite late in the Apple revival and shift to Intel CPUs. Back then, Windows XP was clearly too old, ugly, clunky and misused to be part of *any* high end PC offering. In my opinion, the OEM attempts to improve the Windows XP experience by way of pre-installed utilities were even worse.
The elegant UI and experience that OS X offered was way ahead of what Windows XP and most contemporary Linux distros could offer and that's what helped today's perception of MacBooks and iMacs are fine for their price, unlike many Lenovo, HP, etc that only sell at £300-£500 and therefore cannot have high end parts.
Now there's a lot of web-developer type of professionals who use OS X, helping sustain the perception that modern, trendy, successful, etc, etc professionals go with Apple, while the bad guys on 24 use matte black Lenovos :)