Last week I installed Belltech's 6405 rear lowering shackles. I decided on Belltech after reading reviews praising the rubber bushings and low chance of funny noise, etc.
Honestly I do see a little bit of a difference but not much, regardless it helped get rid of some of the rake so I guess it was money well wasted. lol
No funny noises or anything to speak of, it may just be wishful thinking but the rear feels more solid now in general....who knows.