The current version of the Windows Installer XML Toolset is 3.7. WixEdit doesn't recognize the installed 3.7 WiX Toolset and presents an error message on launch: "Missing Wix", "Windows Installer XML (WiX) Toolset installation is required to run WixEdit. The WiX installation can be downloaded from http://wix.sourceforge.net/. Please download and install WiX and specify the install location in the WixEdit options."
The path has to be set manually, then everything seems to work as with 3.6
P.S.: the URL of the WiX toolset is now http://wixtoolset.org/