"The big question is what's Microsoft's mobile strategy beyond Windows," Rotman Epps said. "It leaves Office open to disruption."

For example, particular threats are productivity suites that, despite lacking the comprehensive feature set of Office, work on iOS and Android devices, like Google's Quickoffice, she said.

Another area where Microsoft can improve is in simplifying the bundling and licensing of Office 365, which now encompasses many options, variables and packages for consumers, SMBs, enterprises, government agencies and schools.

In this area, Google Apps has managed to appeal to customers attracted by its simpler and more streamlined offer with fewer packages and straightforward pricing, said Guy Creese, a Gartner analyst.

"Microsoft should be using the cloud as an opportunity to simplify things and it isn't," Creese said. "It's better than it was, but not as clean as it could be."