I think the virus argument has had its run long before. Sorry David, but I'm with the opposing side on this one. If Mac were more mainstream worldwide, only then could we test its mettle. It seems to me that it would hold up better with its first big worm than Windows XP did considering it's based on BSD, but it's not fair to use the virus argument to praise Mac.
[EDIT]
Inspire, I missed your post with the antivirus.about.com link. I absolutely think those aspects of OS X help it maintain better security, it's just unfortunate that it hasn't been fully put to the test.
I'm run ClamXAv which will scan and update periodically, and have ClamSentry set to watch my download folders.
[/EDIT]
And if you're not worried about upgrading your processor or motherboard more than once, what's the big deal about upgrading Macs? I'll give you that it's a pain to upgrade the mobo and CPU in a Mac, but you said that you shouldn't have to upgrade that . . . ? Hardware arguments have been pointless ever since Apple got smart and switched to Intel.
What's wrong with a Mac that you can't use it for serious computing? I develop Flex-based flash games, Java apps, C/C++ command line tools, and have been playing around with Ruby on Rails, Django, Symfony, Cake, etc. on my Mac and it's been a great experience. I mentioned before that nobody has .NET development and Visual Studio beat if you are able to target Windows as your exclusive platform. No argument against that, I'm loving it. But, if you want to build cross-platform I imagine you'd have more luck porting from Xcode, Eclipse CDT, Netbeans C++, or even MonoDevelop to Visual Studio rather than the other way around.
Also, Mac has its own share of sexy text editors. I have Notepad++, UltraEdit, and other great editors for Windows, and for Mac I have (among many of the same editors on Windows ie: jEdit) TextMate and BBEdit.
And I usually encounter that period of uselessness after startup on Windows more often than Mac. I'm constantly having to run CCleaner and and scan through my process list to make sure something I disabled didn't turn itself back on after startup. On Mac, the only time I've ever had slowdown after login was after installing Butler--which makes sense since it indexes your apps (and I had a ton apps).
And what is "serious computing"? Programming? I think I've made my point about that. Is design not serious computing? I know when I'm producing music I'm doing all in my power to optimize resource usage for it just as I would on Windows or Linux. Is that not serious computing?
And are you really gonna moan about Steve Jobs? I admire him for his business sense and marketing ability, I think he's a douche for telling iPhone 4 users that they're holding it wrong. As long as Apple keeps making products I can enjoy using, Steve Jobs can do what he wants.