[KwasiOwusu]

"But I wouldn't quite say "rocks" just yet"

Its still listed on the Nasdaq, running smoothly and efficiently on Microsoft Windows.
Which is what we are talking about here.

"Even when you have multiple load-balanced, redundant servers, more down time still means more admin time, which means higher TCO"

Bottom line: NASDAQ has been running remarkably well on Windows Server for years, and hasn't been made unavailable due to computer outages that I know of.
If you do know of any, I'll be happy to concede the point.

[antiRepublicrat]

hasn't been made unavailable due to computer outages that I know of.

Of course it won't, because they'll have a large redundant cluster, something IIS also only recently learned to do somewhat decently. This doesn't change the fact that Windows can't maintain the production uptime of a *nix system, so various portions of the cluster will be often unavailable.