It comes with many improvements and new features, my favourites are:
Roslyn is .net’s open source compiler. Open sourcing the compiler means that developers can create their own set of tools and build on the current set of API’s to extend its features. Roslyn has set of Compiler API’s (Diagnostics and Scripting) and Workspace API’s (Code Analysis). The Workspace API’s work great when dealing with custom coding standards and extending the current set of tools built into Visual Studio, while the Compiler API’s can be used to for custom code diagnostics and executing snippets.
It is also really exciting to see that code will be compiled on the fly, warnings and errors will still be brought to the users attention in a similar way, however there will be no binaries being built on build. I’m not sure what this will mean for really large solutions, however for my uses it means coding will be much easier and quicker.
Unified MVC and Web API controllers will make creating rich web apps even easier. Currently they use many of the same names classes, however they work differently, using the same controllers and sharing code will mean less duplication for a developer and a cleaner solution.
JSON Configurations are great when using nuGet packages, currently Visual Studio uses a config XML format to do this, and I personally feel that the move the JSON will make the readability and portability of the code much easier. It’s a shift towards a package model (over libraries)
Tag Helpers sound interesting, I tend to use T4MVC tool pretty heavily though my work, so it may be a slightly harder transition to make to move back to less strongly typed method. However it is nice to see the gap between server side code and front end code reducing.
Microsoft have also gone all cross platform, this includes development (With an android emulator being included in the next iteration of visual studio) and hosting. ASP.net will be able to run on Linux and OSX without the need for a Windows VM. This will be using the Katana Package Modules, which was inspired by the Node Packaged Modules.