leaf spring bushings ...

are greasable shackle & rear leaf spring main-eye bushings worth it? or are the Polyurethane bushings fine?

I would think the greasable shackles would give more flex offroad. The poly ones give less, would stiffin up the ride on road/ handle better. Rubber ones are a good compromise between flexing and handling. Just my opinion though, I'm sure others will have different thoughts...I suppose it depends on what you want your jeep to do best...

Mine are rubber and greasable. They are worn the hell out also. But my junk has been wheeled hard for about 3 years, the shackles were on the jeep when I got it so I have no idea how old they are.