I had a set fitted to my ambulance for 4 years with poly-bush's, I went to Africa and back and a lot of offroading and i never had a problem. I believe they have a lifetime warranty on the chrome work on the rams as well.
as above they had a bad rep for breaking eyes off the shocks but was mainly down to inproper fitting and bushes that did not flex on coil sprung motors(the rears twist away from mount). Sereies have always had quite good reports.
Do note that the 2 inch extra droop may cause propshaft issues when the axle drops fully. Do jack the chassis up and check the propshaft for binding to make sure its ok.
Got the plus 2" es 9000's on my disco married to bearmach springs and havent had any issues, i do get a bit of prop shaft vibration at about 30mph though.