I installed mine this weekend. As stated before, install was a bit of a pain, primarily because of the spring compressor tool. I honestly think I had to crank each one about 500 times per side; arms got a bit tired and the angle was uncomfortable, but not unbearable. Start to finish it took me about 3.75 hours with the first side taking much longer than the second due to the learning curve.
I didn't re-use the rubber spring seat and I've got no squeaks or any other undesirable side affects. I'm on factory ZSP and the perches lowered the front of my car 9/16". I went from being able to get "2.5 fingers" between the tire and fender and now I'm at 1.5 fingers. It's a subtle difference, but I'm happy with the result.
The perches seem to be a very high quality product and tanks to everyone posting their experiences as it made my install much easier!
