If you're still looking for the answer, the best way to open a file in a metro app is to use an execution string like a normal app protocol does. The execution string looks like this:
bingnews:[arguments, can be left blank.]
microsoftvideo:[arguments, can be left blank.]
netflix:[arguments, can be left blank.]
So, to start up netflix, it's as simple as typing in Start netflix:
into the command line.
To find the execution string for an app, go here: Control Panel\Programs\Default Programs\Set Associations
More info and examples can be found here.
http://windowsitpro.com/windows-8/opening-windows-8-apps-command-prompt-or-script
http://www.itsjustwhatever.com/2012/10/28/launch-windows-8-metro-apps-from-a-desktop-shortcut-or-command-line/
PLEASE NOTE: To open an app WITHOUT A PROTOCOL (One not listed in the registry or under "Set Associations") use OP's method:
explorer shell:AppsFolder\[appuid]![appfullname]
The app UID is the folder name without the version number. For example,
4DF9E0F8.Netflix_2.11.0.8_x64__mcm4njqhnhss8
becomes
4DF9E0F8.Netflix_mcm4njqhnhss8
The app fullname is the [App author].[App name]
For example, 4DF9E0F8.Netflix
. 4DF9E0F8 is the author, and Netflix is the name.
Put it all together to get
explorer shell:AppsFolder\4DF9E0F8.Netflix_mcm4njqhnhss8!4DF9E0F8.Netflix