Microsoft on Monday pushed multi-tenant SaaS versions of Exchange and SharePoint out of the beta nest.

Some 7,000 concerns participated in the beta. Now the stuff's available to all comers.

Exchange Online will cost $10 per user a month; SharePoint Online will cost $7.25.

Eventually a browser-only Exchange/SharePoint combo will go for $3 and a Business Productivity Online Suite (BPOS) with e-mail, instant messaging, web conferencing and SharePoint for $15. The IM component is still missing.

Gartner says the collaboration widgetry will compete with Google Apps, which goes for four buck a head a month. It warned, Microsoft to watch out for Google Apps' encroaching e-mail widgetry not to mention its productivity wares.

The researcher is expecting 20% of enterprise e-mail seats to use SaaS by 2012, up from 1% last year.

Microsoft figures customers can save 10%-50% on infrastructure and staffing by moving to its Online Services.

It's sold some 500,000 seats so far to large companies such as Pitney Bowes, Philips and Eddie Bauer, which dumped Lotus for Microsoft. Lotus is reportedly often what early adopters are dumping.

Microsoft's got a bunch of new migration tools now like assessment and planning and has started pushing the 1,500 third parties signed to deliver custom apps for its Online Services into the spotlight, with 100 more a week reportedly being added.

Gartner warns early adopters that it's not a piece of cake and to expect "challenges with stability, contracting, data migration, integration, security and legal issues."

Microsoft is promising to beta a multi-tenant Office Communications Online next year as well as a subscription service to manage and secure desktops. And of course everyone's standing by for the promised Office Web Apps drop.

See http://microsoft.com/online.