Microsoft Visual Studio 2013 Update 4 Release Candidate (RC) is now available. Release Candidate is basically a candidate build for release and a fancy way of saying 'beta.'
CodeLens is a tool that provides references, changes, related items, and unit cases for the code you are working on -- without requiring you to navigate away from it. It now has reduced data storage requirements with Team Foundation Version Control. Duplicate CodeLens data stored in the Team Foundation Server has been removed.
C++ has received a GPU Usage tool in the 'Performance and Diagnostics' tools to help determine if the CPU or GPU is the bottleneck of your application (which is programming terminology for what is slowing down your application, like a bottleneck does for the flow of a liquid). This tool can be used for DirectX applications, including Windows Desktop and Windows Store apps.
Microsoft ASP.NET and Web Tools receive updates for JSON and HTML editors. Azure WebJobs has received features aimed at making it easier to build, deploy, and debug WebJobs. Applications Insights Tools for Visual Studio have received performance improvements, bug fixes, improved integration with workflow to publish to Azure websites, and improved solution integration and project detection.
One of the favorite additions is Git support. Developers can use pull requests to merge and get feedback on their code. Developers providing feedback can see changes, leave comments, or simply a 'thumbs up.'
These are only some of the updates in the Release Candidate, and they give a pretty good impression of what the final release of Update 4 will look like. You can check out the full details here.