TT: Your steering will wear out faster, but some have had no problems (I haven't yet). It probably depends a lot on how hard you are on the vehicle.

Shackles: Some claim that these cause the rear leaves to flatten over time. The only logical argument on this is that I've heard is that when the tire stuffs offroad the leaf will have to flex more (due to the longer shackle), which could possibly lead to sagging. That's the only argument that I've heard on the subject with any merit at all, and it may be true (though I'm not convinced). Other than the possible extra flexing, the spring doesn't have any idea that the body has moved 1.5 inches further away. I've had mine on over a year and still don't have any flattening. I figure if it does eventually flatten I'll get AALs to bring it back.