The brackets do a couple of things. First, they correct the caster, bringing it back into spec. The light caster you have after the lift makes the steering flighty. They correct the geometry of the control arms which helps handling and braking. In short, they make a lifted Jeep drive like a stock Jeep.
I run that lift with those tires. The brackets are the best $120 I've spent on the Jeep. Made a good lift a great lift. If you feel the flighty steering and brake dive, get them.