Cloud integration and subscription licensing make Office 2013 is a landmark release for Microsoft. Also, it's the first upgrade to the servers behind the Office 365 services.
The new Office 365 plans are a simple and cost effective way to get access to new features in desktop Office 2013 and new versions of Office servers, without the work of running your own servers.
The new administration interface makes the service easier to work with, whatever your level of expertise, and SharePoint and Exchange Online have major new features.
Existing Office 365 users have to wait for Microsoft to schedule upgrades to their accounts (and some early migrations have caused issues with SharePoint online). Also, Microsoft still has to prove it can offer meaningful improvements on a regular basis, like taking advantage of Skype and Yammer inside Office 365
For smaller companies that will appreciate the new, simpler interface, Office 365 is a reliable service that integrates email, document sharing and conferencing almost seamlessly with the new desktop versions of the Office software. It also has powerful options for larger businesses.
The savings from putting commodity IT in the cloud and still being able to integrate with on-premise servers through Active Directory and hybrid Exchange deployments could make the combined subscriptions for server and desktop products very attractive.