In the great tradition of no-brainers, Google today opened the virtual doors to its Apps Marketplace, inviting us all to download, try out and purchase complementary services to its core productivity applications and communications suite.

I've been like a dog with a bone for quite some time when it comes to Google Apps. People often forget that Microsoft Office is one of the great cash-generating franchises in modern business history so anything that challenges the status quo* tends to be worth watching. Most challengers, even the better ones such as such as OpenOffice and Lotus SmartSuite, have simply not been good enough, even if Microsoft politics like playing 'Who moved my file format?' have not helped. Now, however, with the web browser established as the ground zero of desktop computing, and with Google inching forward in terms of features and build quality, the challenge is very serious indeed.

Don't take my word for it. Listen to companies that have made the big switch. Talk to the people in newspapers, whether it's The Guardian on your left or the Daily Telegraph to your right; to universities like Westminster or Leeds Metropolitan; to large risk-averse companies like Rentokil or Taylor Woodrow or Valeo. Or listen to the people thinking about a move: I meet new ones every month. If you're still not convinced, take a look into the eyes of your Microsoft rep. They recognise the seriousness of the threat, I think.

And of course, every Google success doesn't just hurt the Microsoft Office hegemony; it also undermines Microsoft Windows because if your company runs Google Apps for basic automation and messaging it becomes harder to justify having a premium-priced operating system for all your users. Of course, Microsoft has other successful products but these are the twin pillars that support its very structure. As for buyers, they're just happy to have a choice and even if they elect to stay within the Microsoft fiefdom, they now have a new Pugil Stick to help them negotiate terms.

Google Apps is nice, cheap, improving in quality, highly extensible (as the Apps Marketplace shows) and its position gets better with every improvement to communications bandwidth and availability.

Of course, Microsoft remains dominant for now and, while it's not fashionable to say this, Microsoft Office is a fine product that invented or refined many of the best usability shortcuts that so many of employ without thinking. It also has the support of a planet's worth of ISVs, partners and people who know the product backwards. But Office is old and it's expensive so we should all -- with the exception of Microsoft shareholders -- wish Google Apps well. I feel a change coming on and it's not going to be nice for Steve Ballmer.

*I don't mean the dreadful band with the three chords, obviously.