I have used a lot of IDEs over the last 10 years. I have to say that Visual Studio has always been one of the best to use.
I will give some background to help with this review. I have been using Visual Studio since VS 2005 and have used every version since. I am a .Net developer and focus on C#. I have over 6 years experience with this line.
This is by far the best Visual Studios I have used. One of the things that Microsoft focused on in this version was usability. They redesigned the entire UI and threaded most of it. It runs so much faster. It does take a little getting used to after using previous versions, but I am able to find things so much easier now. There is also a change where most things no longer launch a blocking window for every option. This has all been moved to the sidebars.
There has also been a lot of work done with the Solutions Explorer. This is a very welcome change. They have moved the object explorer functionality to the Solution Explorer. You can now open a tree view under a class file and see all properties, methods and other information about the class without having to open the file. This is very nice if you can't remember names and don't want to bounce back and forth between files. You can also open multiple solution explorers in other windows without having to relaunch Visual Studio.
Testing has also been improved. Visual Studio 2010 really had some nice unit testing features. Visual Studio 2012 has added support for external testing frameworks. They have also improved the experience with the MSTest framework built into the application. Everything has been moved to a sidebar and easily accessible. There is also a very nice code coverage feature that will color code your source. Another nice feature is the datasource features available. You can store information needed for tests in either a database or xml file accessible by the test framework. This allows you to easily store one or more inputs for a test and expected outputs.
There are so many other tools that go along with this release that I can't possibly get into them. I have talked about the features that I use most, but there is so much more to it. Team Foundation Server integration (there is also now a cloud solution for this), code analytics tools, etc.