One year on: Microsoft Office 365 success remains unclear

"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."