On the face of it, Microsoft without Bill Gates seems a bit like The Simpsons without Homer. This isn't meant to be a cruel comparison; my point is simply that the two 'people' are largely synonymous with the vehicle of their fame.
Of course, the truth is that the world's most significant philanthropist is hardly likely to disappear from public view anytime soon and the IT industry will move on without missing a beat. Do you know the founder or CEO of Coca Cola, McDonalds or General Motors? If you do, you're in a small minority and it's in some ways a significant milestone that the man behind the world's most famous technology company will no longer be a full-time employee. IT is indeed growing up.
And yet, Gates leaves Microsoft at an incredibly important time. The company's Windows Vista operating system has been arguably its most troublesome child, widely criticised and snubbed by many users; next-generation companies like Google are changing the game of applications delivery in ways that make it difficult for traditional players to compete; anti-trust legislation, particularly in Europe, continues to chip away at market strangleholds; Yahoo! has so far obstinately refused to jump into bed despite a very public courting; and there are exciting new 'co-opetition' battles to be fought in areas like virtualisation and unified communications.
The plates are spinning and there's little or no time to catch a breath. Having dominated its market for a couple of decades, Microsoft is having a mid-life crisis in which Yahoo! could be seen as its much younger secretary or the red convertible sports car.
Gates has been a famous crystal ball gazer over the years - he warned of a major backlash against the Internet, four years before the dotcom bubble burst and wiped billions off the stock market, and has frequently forecast accurate changes to the ways we engage with technology - but it would be fascinating to know what he (honestly) thinks about how Microsoft's battle with Google will play out.
Gates' two chief lieutenants - chief executive officer, Steve Ballmer, and chief software architect, Ray Ozzie - are the men charged with transitioning Microsoft's dominant position in the IT software market into a brave new world of Internet advertising and online services. It's a big ask because a whole new generation of competitors led by Google have got the jump on them but, on the other hand, you don't need many fingers to count up all the times Microsoft has put its communal mind to something and walked away with its tail between its legs.
If all doesn't go well for Microsoft in the years ahead, you can bet Gates will take a lead from Michael Dell and jump back into the driving seat. Something tells me he just wouldn't be able to help himself.
In the meantime, whatever the immediate future holds for Microsoft, Gates has plenty to keep him occupied with lofty ambitions to improve global healthcare and feed the world's poor. No matter what your opinion of Microsoft, I'm sure we all wish him well with those.