I call out this stupidity when people try to prop up Mac OS X market share, so I'll do it now as well: Despite what you may have read (and, really, Gregg Keizer should know better), Windows 7 has not yet surpassed Mac OS X's market share. The reason is simple: Market share is sales over a set period of time (usually a quarter in the case of PCs). And we don't know what Windows 7 sales are like yet. Make no mistake, Windows 7 market share will surpass that of OS X by the beginning of 2010, obviously, when the first quarter of Windows 7-based PC sales becomes available. It's literally just a matter of time.
But it's not 2010 yet. So we don't know what PC sales are doing. In the meantime, what we do have, as always, is "usage share as measured by which OSes people are using when browsing to certain sites on the web." This is not market share. It's not even usage share. It's just what I say above in the quotes and nothing more. You can make generalizations about these worthless numbers if you want. But you cannot morph them into market share or usage share. They're just not representative of either.
So while I'm OK with that fact that more people were browsing certain parts of the web using Windows 7 than were OS X for a certain time period last week, this doesn't mean anything.
And I wish others wouldn't promote this stuff as news. It's certainly not that either.