The preview includes improvements in IntelliTrace, CodeLens, debugging and testing tools. Update 3 allows users to now debug x86 applications that are built by .Net Native (Project N).
The preview also includes the ability for Windows PowerShell or the WIndows PowerShell Desired State Configuration (DSC) feature to deploy and manage configuration data -- something Microsoft is touting as easing configuration and management of on-premises and Azure virtual-machine-based cloud infrastructure.
The Visual Studio team has been delivering more rapid, near-quarterly updates that include both fixes and new features for the past couple of years. The team isn't saying when to expect Microsoft to deliver the final version of Update 3.