they can unload when hill climbing which supposedly makes for an... interesting sensation. they've been around a while now and no one I know that used them still has them.
on a similar topic, MJs don't need frame braces like XJs do. they are trucks capable of hauling 2200 pounds in the bed. they are plenty strong. unless the frame is rotted and needs help, I would save my money.
rocker guards are needed though. there's a lot of wheelbase there to protect.