pro comp is very reputable but not with our jeeps. its pretty much hit or miss. some complain about sagging springs, some complain of the ride quality...its just internet parroting. a few local jeepers in my area have em and they performed exceptionally well in minor offroad course.
if you have a jk, a 2.5 lift coil lift will suffice. a rear trackbar relocation bracket, coils, bumpstops (if ur planning on running 35's), and of course shocks. there are many other reputable brands that are of higher quality. i'm not saying to stay away from pro comp, but there are others that have better reviews.
if your planning to stick to pro comp 4, you may run into driveline issues when offroad. option a... get an exhaust spacer, option b... get a y pipe, option c... get an aftermarket driveshaft or option d... wait till you need to replace it.
and...pro comp 4' is comparable to a rock krawler 2.5 in terms of height...not quality.