If there's a way to lock them in place, for normal driving, that's be better. Otherwise, I could see all kinds of stability issues on the highway, including the before mentioned braking issue.

So, they give a little bit extra droop, but that's about it. Also seems like you're putting a hellofalot of leveraged stress on parts that might not survive it.

Also, seems like it might cause some major wheel hop issues.

Maybe they are better somehow with the Jeep's shorter wheelbase and more weight over the rear wheels. Also, the one's I've seen advertised for the Jeeps include locking pins to make them act like traditional shackles on the street.