I've just tried this on the Super Nexus/GPE edition rom by joe-user.
After reboot my applications kept force closing.
Upon a second reboot, i was placed in a bootloop also - safestrap disappeared.
I'm in the process of ODINing my phone back to stock and starting over again.
I'm assuming this isn't friendly with the ROM and I advise those on this particular ROM to stay away from it.
Samsung Galaxy S4 - i337 LTE
OS: Google Edition S4/ Pure Nexus Edition
Kernel: Stock (SafeStrap 3.72B with Viper's Magic Tool)