Anticipating Wednesday's launch of Microsoft Office 2010, Google on Tuesday encouraged Office users to consider an alternative to paying Microsoft for an upgrade: upgrading Office by using Google Docs.

"If you choose this path, upgrade means what it’s supposed to mean: effortless, affordable, and delivering a remarkable increase in employee productivity," said Matt Glotzbach, product management director for Google's enterprise group, in a blog post. "This is a refreshing alternative to the expensive and laborious upgrades to which IT professionals have become accustomed."

Having just completed a major revision of Docs and Spreadsheets, Google wants to make sure that businesses give its Web applications serious consideration.

The company recognizes that most companies use Microsoft Office and has positioned Docs as a way to enhance Office with collaboration and sharing features. It wants users to rely on its Web apps exclusively, of course, but it knows that change of that sort comes gradually.

Glotzbach's argument that Google makes Office better -- enough that Office 2003 and 2007 customers would have a better experience by adding Docs for collaboration and sharing instead of paying for an Office 2010 upgrade -- doesn't sit well with Alex Payne, director of Microsoft's online product management team.

In a blog post on Tuesday, Payne challenged the notion that Docs enhances Office.

Google, he said, is "claiming that an organization can use [Docs and Office] seamlessly," he said. "This just isn't the case."

Payne argues that the way Google imports Word documents changes their layout, in contrast to Microsoft's Office Web apps.

However, this criticism may be less valid now that it has been in the past -- one of the major aims of the Docs revision that Google completed last month was to assure the fidelity of imported documents.

In any event, Microsoft is moving online in a big way. Google has a real fight on its hands.