The GUI for Virtual Package Editor seems to be robust. It has a good interface that allows you to easily modify an existing .appv file. You can add/remove files and registry keys fairly easy. However, Admin Studio must be installed on Windows 8 or Server 2012. Also, if you plan to use ACC, your target VM’s must be Windows 8 or Server 2012 as well to sequence or even edit a package.
When your enterprise is migrating to Windows 7, this can cause issues. Flexera will tell you to sequence on Windows 8 and publish to Windows 7. This would be beneficial only if the application was completely isolated to its installation directory. So capturing on Windows 8 and streaming to Windows 7 would not be a good practice. I’m sure you will get lucky with a few applications. Most packagers have great success with packaging on legacy systems and publishing on later operating systems. This has been a standard practice since 2001 when enterprises started migrating from Windows 98 to Windows 2000.
With the latest issues of the 2013 Repackager compiling and leaving out files and registry keys captured in the IRP, I just use the Microsoft Sequencer. This does an adequate job, and it is free.
As for the Repackager issues, the issues are supposed to be resolved with 2013 R2. However, it has it’s own issues as well. You can read about them at https://roadmaptech.com/?p=388.