VSIX registration and unregistration issue

I'm having some problems when registering and unregistering an extension in Visual Studio 2012 / 2013. The issue is the following:

1.- Register an extension:

vsixinstaller.exe myvsixpackage.vsix

A directory is created in my local folder, under C:\Users\xxx\AppData\Local\Microsoft\VisualStudio\12.0\Extensions.

2.- Unregister the extension:

vsixinstaller.exe /u:myvsixID

This unregisters the extension, but it does not remove the extension assemblies; When I restart Visual Studio and plugins are loaded, the files are removed. It seems that the extensionsis marked to be removed later.

3.- Register the extension again.

vsixinstaller.exe myvsixpackage.vsix

I get the error: "This extension is already installed to all available products".

But if I open VS2013 the extension is not there. Eventually I cannot even unregister it (VSIX installer says that the extension was already uninstalled) and I have to remove the directory manually so that I can register my extension again.

Is there any workaround for this? Is it a bug? Am I doing something wrong?