Mac - Audio/video/graphics development or uni/college students who use Word & Facebook and want to look cool doing it
Linux - Geeks and some servers (web or virtualisation)
Windows - Gaming, Enterprise (Exchange/SQL/etc), everything else not covered by the above
The whole "Macs just work" thing is an absolute lie, I crashed a Mac yesterday just going into the Network settings of a Powermac running Final Cut Pro at the same time. Search any user forums for audio development and you will find people cursing Apple daily. Best example I can remember was a glitch in Core Audio's native Firewire driver that caused random offset latency for years and it took a partnership with Apogee that had the same problem for them to fix it and It still took over 12 months to address. Last I checked it still wasn't perfect, but managable.
Never argue with idiots
They bring you down to their level and then beat you with experience
