Yesterday Microsoft released the new Update 3 for Visual Studio 2012. When Visual Studio 2012 was launched back in September 2012, Microsoft promised to provide more frequent updates to Visual Studio: in November Visual Studio 2012 Update 1 (VS2012.1) and in April Visual Studio 2012 Update 2 (VS2012.2). Both of these cumulative updates contained significant new features sets, spanning areas such as Windows desktop development, Windows Store development, line-of-business app development, SharePoint development, agile planning and teams, quality enablement, and more.
Visual Studio 2012 Update 3 (VS2012.3) is an incrementally smaller update than its two predecessors: it includes some new capabilities, but is focused primarily on bug fixes. The update will install on top of the previous updates (if already installed), or can be installed on the RTM release and still get everything from those previous updates.
It is important to install this update if you need to be able to "round-trip" projects between Visual Studio 2012 AND Visual Studio 2013, or if you want to run Visual Studio 2012 on the freshly released Windows 8.1 Preview.