When TJ's are lifted using the stock suspension mounting points, the control arm angles are increased, which causes the front axle to have to move forward and up causing the ride quality to be somewhat harsh. Another negative aspect of this modified factory geometry is that the wheelbase is shorter than delivered from factory. This, combined with a stiffer spring rate, makes it much tougher for the axle to react to bumps as it was designed to do. The arms bolt to the axle in the same location, but your frame mounts will need to be cut off. This allows the use of the long arms, and decreases the angle at which they live.
Word is, even with the tall springs, the road ride is as good as stock.
We will see. Well, RE does focus the benefits of this kit on the street, but they were also quick to point out that off-road, the Jeep will feel more balanced and stable, and respond better to situations where the tire may stick up against a vertical rock. I had approached an obstacle only to find that when gas was applied, the entire Jeep lifted, wanting to climb, but the tire on the rock moved down and back instead of up and over as the spring stretched and unseated. With a tall lift, turning left slightly and punching the gas can cause the driver side front tire to come off the ground. Pretty scary if you aren't expecting it.