Is it worth it? Depends on your wants/needs/usage, but I'ma say probably not...
I compete in time trials but my BRZ is also my daily-driver. I am about to install Whiteline rear subframe bushings after feeling lateral rear squishiness at the track, but that's all I have planned for aftermarket polyurethane. I think this should let the rear suspension move properly without as much lateral monkey-motion. I'm not too worried about replacing the suspension bushings with poly for a few reasons, mainly because I'm lazy but also I don't think my street/track setup is stiff enough to benefit greatly vs. a dedicated track build.
Here's a good thread on the subject:
https://www.ft86club.com/forums/showthread.php?t=106000