"When you are managing 60,000 desktops in 100 countries, however, the rules change."
Indeed. With their record at this sort of scale I'd be worried about using Microsoft. And even considering their massive discounts to big business users it would be expensive - though I would write it off as a business expense and get the ordinary tax-payer to subsidise me (and Microsoft).
"You can get away with all sorts of things in a small business, including many unconventional IT policies..."
I hardly think Linux per se qualifies as unconventional nowadays - should we all then be restricted to commercial UNIX or Microsoft? Would it be "better" if I was using FreeBSD (which I considered) or are only commercial offerings acceptable?
The fact is that just about any modern OS is as good (or bad) is its implementation in a business. Crap sysadmins, slack security and lazy policies will make any system liable to instability, corruption and crashes no matter how much money you have paid for it.
Mac