I was getting very loud suspension noise from up front and I thought my JRZ shock(s) were defective. One BMW dealer said the right front shock was faulty but another ( Dinan dealer) said it was fine and that the sway bar bushings were shot causing the noise. I have Eibach sway bars so I had to find replacement poly bushings. NOT EASY. I ended up getting a set from Tire Rack with a spare for future. While at it I bought Powerflex bushings from Beastpower for the thrust arms and control arms. Noise is gone and the handling seems quite tight. It is tough for me to feel a huge difference on the street as I have not pushed the car yet. Going to LPR on 4/5 and will see then. Since it was at the dealer for the shock/sway issue they did the work. I think it was around $300 or so.
FWIW, Powerflex are very popular with the M3 crowd for replacing the Rear Trailing Arm Bushings. RTABs in e46 M3s are a weak point, so a lot of people go to Powerflex when theirs fail, or sometimes even before they fail. Not many complaints about noise or harshness so long as you lube them very, very well with copper type anti-seize. On the other hand, a lot of M3 owners will put up with quite a bit more noise and harshness than most of us would. Same benefits, though, of far more precise steering and more predictable and crisper turn-in.