Well I don't know if it's worth specifically buying a jailbroken PS4 or just buying one on lower firmware or even current firmware and waiting for a release. The real jailbreak for online is coming soon.
It all depends if any of the features appeal to you, here's some reasons you may want to use one;
PS4 JB Features;
-Be able to play games through PKG installation
-Use offline mods for COD/GTA etc.
-Test homebrew applications
-Use tools to get offsets etc for games
Hopefully we'll see some more features added in the future.