Here is my review of performance. VERY nice ride quality with a soft, forgiving nature when going over road imperfections (i.e. potholes, expansion cracks, etc.) and awesome firmness with control at higher speeds and when cornering. In comparison to the Sachs that I installed on my '00, I have to say I prefer the Koni and will say the same about the OE setup the Koni's have replaced. If not for the other technical issues, I seriously would've given this product a 5. I hope you find this review helpful...
My next comments are more about the advertising and lack of better instructions. Basically Koni states that the shocks are vehicle specific but if I hadn't been paying attention, would've installed the rears incorrectly. There are 3 "settings" for the spring perch and mine had the C-clip on the middle setting, which is TOTALLY incorrect for my '03 BMW 540i M-sport. Had I not noticed this, I would've had to remove everything to correct an incorrect ride height. Fortunately I noticed and corrected the issue before the final install.
AFAIK, the adjustables come set to full soft and I noticed that the front felt too mushy. Fortunately the fronts are adjustable WITHOUT having to remove the assembly or I would've been screwed. I turned the front adjuster one full turn and the difference was noticeable. Less mush, less dive and more precision up front...I may dial them up another notch to see how I like it. Unfortunately the only way to adjust the rear shocks is to remove the entire assembly down to the bare shock again...RPITA and a bad idea IMO.
The instructions suck! Literally cartoon drawings with no words and parts that don't transfer from the original to the new. Still not sure if I put the foam and plastic washers provided in the right place but there aren't any odd noises and everything seems to be functioning well.
Overall I think these are great quality and provide excellent performance but be aware that you may have to write down a list of questions to ask before you settle down to tackle the task on a weekend when you can't contact anyone about technical issues...