Google Thursday planted its flag on the shores of Microsoft's Fortress Office, finally opening up shop to sell the anticipated commercial version of its comparatively rudimentary web-based productivity software, aiming it at the big enterprise, the source of much of Microsoft's power and revenue.

It's calling the stuff Google Apps Premier Edition and put an annual price tag of $50 per user account on it, undercutting - but not by ridiculous amounts - what large accounts wind up paying Microsoft for Office.

However, Google claims it is so cheap it's a "no-brainer to try it out." It's expecting large deals. We'll spare you Goggle saying it's not competing with Microsoft. Office is estimated to have about 450 million users and with Google in the picture Microsoft may have to do some more discounting.

The bundled widgetry so far includes Google Docs & Spreadsheets, its word processor and spreadsheet programs, Gmail e-mail, the Google Calendar, Google Talk instant messaging, VoIP and a Start Page for creating a customizable home page on a specific domain. Gmail as of Thursday also supports the Blackberry.

Google has been giving most of this stuff away for free since last August as the ad-supported Google Apps Standard Edition and Google Apps Education Edition and claims upwards of 100,000 small businesses and hundreds of universities are using it.

For the money, the Premier Edition includes 24x7 phone support and 10GB of storage, five times what free users get or according to Google 100 times the average corporate e-mail box.

It also includes what Google calls a new set of administration and business integration capabilities like APIs for data migration, user provisioning, single sign-on and mail gateways as well as SLAs promising 99.9% Gmail uptime.

It's made advertising optional on the Premier Edition. Google probably needs to get less dependent on advertising for its revenues.

Google says it will continue to offer the free services.

Google says Proctor & Gamble, General Electric, Prudential Preferred Properties and the like-minded software-as-a-service CRM hotshot Salesforce.com are giving it a spin.

Adding insult to injury, P&G, which is where Steve Ballmer used to work before Microsoft, has signed up as a so-called charter enterprise customer to help shape the software's functionality.

Google, for instance, is believed to working on a PowerPoint-like program code named Presently.

In exchange for the collaborative features of Google Apps, Google is asking corporations to do what at least used to be considered unnatural and put their documents on another company's servers. For that reason, it's assumed interest will be pretty much limited to lower-level employees.

Of course, the stuff also doesn't work if there's no Internet connection and Google just patched a hole in its Google Desktop software - the stuff that lets you search your own drive - that hackers could have exploited to access confidential data and turn your PC into a zombie.

Google's timing was noticed. It's less than a month since Microsoft began pushing Vista and the new Office 2007 at all levels of the market.

Google Apps is available in French, Italian, German, Spanish, Chinese, Japanese and Korean and Google says Essilor and Mediametrie in France signed up as early adopters.

See http://www.google.com/a.