SQL Server Compact 4.0 SP1 has now been released as a web download (it is also included and installed with Visual Studio 2012). The release version is 4.0.8876.1
This release adds support for Windows 8 and Visual Studio 2012. In addition, it also includes some bug fixes and a new feature (so far undocumented), as I have described here
I would say it is a recommended upgrade for anyone using version 4.0.