Microsoft has supported hybrid directory architectures for years but it’s always been somewhat complicated to setup and required multiple services and services. We just implemented Office 365 in a hybrid architecture and the most complicated aspects are the integration of directory services, especially when including Exchange and Lync on top of Active Directory services.
Given that Microsoft controls most of these technologies, it shouldn’t really as complicated as it is – this is primarily because of legacy reasons and the evolution of all these various federations scenarios.
Microsoft has released a new tool in preview (e.g. it’s not Production support just yet) called Azure AD Connect that centralizes and simplifies the hybrid directory scenario of connect your on premise AD with Azure AD. It’s available for download here.
This tool will replace DirSync, Azure AD Connect and Azure AD Sync as a single centralized tool.