One problem with PlayStation 4 is you can not downgrade the system 'firmware', so those on v6.0 or v5.5, can not go back in time on their PS4 consoles and enjoy basically the totally open v5.05 exploitable PS4 firmware, but that could change in the near future as recently @LightningMods_ gave out a link to a 'pastebin' that contains allegedly a bunch of useful 'keys' from the PS4 SYSCON chip that controls alot of the PS4 system boot-up and checking of the signed PS4 firmware files, and other checks.
FW_AES --> 5301C28824B57137A819C042FC119E3F
FW_CMAC --> 8F215691AC7EF6510239DD32CC6A2394
PTCH_AES --> EF90B21B31452379068E3041AAD8281E
PTCH_CMAC --> 95B1AAF20C16D46FC816DF32551DE032
RL78_ID --> 3A4E6F743A557365643A
Click to expand...
For more in-depth news coverage on why this release is so cool and important to the PlayStation 4 Scene, check out Wololo's post which is linked below.