For the best part of the last 20 years, pundits have reported on challengers to Microsoft Office and Exchange, the hugely powerful and lucrative franchises that sit alongside Windows in the underpinnings of the world's biggest software company. Most have failed to survive, never mind prosper, but the latest web-based challenger from Google seems to have some legs.

Office has long had over 90 percent market share in desktop productivity suites and Exchange is the default option for firms setting up email, collaboration and calendaring systems, having sped ahead of the original groupware giant, Lotus Notes. These are the lynchpins of the modern enterprise and many of us spend more time looking at these programs than we do with our loved ones. We know their menus, options, shortcuts, shortcomings and occasional eccentricities and we choose to either delight at the usability resulting from millions of lines of programming code and man hours, or despair at bloated incompetence, vulnerability to security compromises and proprietary lock-in.

If users get to know Office and Exchange pretty well, so do CIOs and their teams. This is expensive software and each new version typically requires more expensive hardware. These programs might not be strategic in the sense that SAP is strategic to the operations of a business's back office but they are omnipresent and represent that awkward category of software that gets noticed by mouthy users and opinionated executives. As Robert Whiteside, Google Enterprise head of UK and Ireland, puts it, Office is "mission critical without adding a lot of difference to companies".

We should know better having seen the likes of Lotus Notes and SmartSuite, WordPerfect Office and GroupWise, Corel and Novell fail to topple Microsoft, but it's hard not to get excited by the latest challenge to the Microsoft hegemony, Google Apps.

Why? First, because Google is so well funded, with a market capitalization in excess of US$120bn. Second, because Google's brand currently has luster that even Microsoft cannot match. Third, because it would appear that business computing is edging towards a cloud-based model where more and more applications reside on the web and the user interface is the browser. Fourth, because web-based systems have intrinsic advantages such as spread cost, reduced admin and no need for corporate servers. Fifth and most interesting, because Google has started delivering evidence that sizeable businesses -- and UK businesses at that -- are willing to take its bait.

Two deals this summer have made the world sit up and take notice. First, construction and facilities management firm Taylor Woodrow said that it had deployed about 1800 seats for Google Apps after a pilot that ran from November 2007.

The deal will provide "a step change in how we use email in the organization", says Rob Ramsay, Taylor Woodrow IT director, by providing users with a Google-hosted service that replaces a legacy HP OpenMail system that was front-ended by Outlook.