I can confirm this. Even with full permissions I get "More permissions are needed to perform this action" when I try to create a new file. I can delete (move to trash) files just fine though, can't edit anything. Will investigate further later.
P.S. C:\Program Files>icacls windowsapps /t /c /q /reset seems to fix issues if your metro apps stop starting
Samsung ATIV S GT-i8750 - Interop unlocked
Samsung Omnia 7 GT-i8700 - Full unlocked custom ROM
Samsung Galaxy S GT-i9000 - CyanogenMod
Microsoft Surface RT with Windows RT 8.1
Past devices: Nokia 3310 > Nokia 3510i > Nokia 7250 > Nokia N81