VS 2015 Update 1 is now available for download, including the updated Community edition. The VS 2015 Update 1 Redistribution packages are also available (x86, x64), as well as the Remote Debugging Tools (x86, x64, ARM). For more information, see Brian Harry's blog, the Visual C++ Team blog, and the Visual Studio Team blog. Be sure to read the MSDN page as well.
Compiler and CRT
VS 2015 Update 1 includes a new version of the C/C++ compiler (19.00.23506). There is also a new version of the C/C++ Runtime (14.0.23506). Here are a list of STL fixes included in VS 2015 Update 1. The new compiler also includes support for the C++11 language feature Expression SFINAE.
Note that VS 2015 can target Windows 10, Windows 8.1, Windows 8.0, Windows 7 Service Pack 1, Windows Vista Service Pack 2, and optionally Windows XP Service Pack 3. The Visual C++ 2015 REDIST does not support Windows 7 RTM, Windows Vista RTM, Windows Vista Service Pack 1, Windows XP RTM, Windows XP Service Pack 1, or Windows XP Service Pack 2 as these platforms are all outside their support lifecycle. See KB2661358.