In May, Microsoft announced that it had struck a deal with the Catholic International Education Office to roll out Office 365's education edition to about 4.5 million Catholic school students this year.
Another recent big win was hardware store chain Lowe's, which will roll out Office 365 to 200,000 employees in 1,745 stores and corporate offices in the U.S., Canada and Mexico.
Office 365 has also bumped Google Apps from some accounts. Brazilian clothing store chain Renner adopted Google Apps in 2009, but down the line got disenchanted with it and recently decided to replace it with Office 365.
The Microsoft suite is better suited to Renner's plan to link its cloud email and collaboration platform with a variety of third-party, on-premises transaction systems and enterprise applications, said CIO Leandro Balbinot.
"At the end of last year, we realized Google Apps wasn't complete enough for that evolution," he said, adding that Renner historically hasn't been a big user of Microsoft products.
The company is now in its first phase of Office 365 deployment to about 2,500 employees, and will later expand the project to cover about 10,000 users, he said.
Microsoft did well to design Office 365 with hybrid deployments in mind, Osterman said.
Some companies are more comfortable keeping certain email and collaboration software on-premises, and it lets Microsoft build on its large installed base, he said.
"That'll work to Microsoft's advantage," Osterman said.
Industry analyst Rebecca Wettemann from Nucleus Research concurs. "Most businesses are used to Office and Outlook, and this hybrid approach lets them take advantage of the economies and flexibility of the cloud while working on the environment they're comfortable with," she said.
Although Office 365 applications offer a subset of the functionality of the on-premises versions, that subset has been more than adequate, Wettemann said. "The core functionality is there," she said.
Another particularity of Office 365 is the broad variety of bundling options Microsoft offers, which some have suggested could be counter-productive and confusing to prospective clients.
With its various options, Office 365 is certainly more complex to understand from a licensing perspective, but at the same time it offers customers more flexibility to mix and match versions to better suit different types of users, IDC's Fauscette said.
"It's not the simplest thing, but in general, people have gotten it," he said. "The channel partners are really good about working with the customers and helping them decipher the details."
Juan Carlos Perez covers enterprise communication/collaboration suites, operating systems, browsers and general technology breaking news for The IDG News Service. Follow Juan on Twitter at @JuanCPerezIDG.