No, it's not true, and it's ridiculous.
Both Windows and OS X have certain advantages and disadvantages.
It's true that Windows is generally the preferred install on most business/enterprise boxes. For some reason, this leads people who work in such environments to assume that Windows=serious!work! because it's their work, so clearly Macs are toys.
This blatantly ignores other professions and work conditions under the false presumption that enterprise office work (or other areas where Windows is preferred) is the only kind of "serious" work.
You even mentioned one area, e.g., graphics design, where Macs are big. Does that mean graphics work isn't "serious" work?
Sucks for them, I guess. 
This is definitely a big one.
If I want to run serious code on my department's serious Linux servers, I can ssh in from any default OS X or Linux install. Not so much from a default Windows install, and the programs that allow it just aren't as elegant as working in *nix natively.
I'm tempted to find a joker.jpg for this serious post, but I'm too lazy.
Both Windows and OS X have certain advantages and disadvantages.
It's true that Windows is generally the preferred install on most business/enterprise boxes. For some reason, this leads people who work in such environments to assume that Windows=serious!work! because it's their work, so clearly Macs are toys.
This blatantly ignores other professions and work conditions under the false presumption that enterprise office work (or other areas where Windows is preferred) is the only kind of "serious" work.
You even mentioned one area, e.g., graphics design, where Macs are big. Does that mean graphics work isn't "serious" work?
It all depends on your arena I suppose. For a lot of scientific computing tasks, the UNIX backing in Mac OS is starting to make it the preferred platform (generally "Use Linux or a Mac") over Windows.
This is definitely a big one.
If I want to run serious code on my department's serious Linux servers, I can ssh in from any default OS X or Linux install. Not so much from a default Windows install, and the programs that allow it just aren't as elegant as working in *nix natively.
I'm tempted to find a joker.jpg for this serious post, but I'm too lazy.