I do a combination of road racing and some autocross with my car. This one is also my daily driver.
As for rear end mods, I have koni single adjustable dampers, H&R "Race" springs, strano rear sway bar, Fays2 Watts Link, and whiteline relocation brackets.
I actually bought this one used from a fellow racer for $300. When I bought it, I was running ESP, and they had yet to change the rules to allow for a differential cover mounted watts link (which is why I did not buy the Cortex link). I do like this design because it really does allow for a unique suspension characteristic in that it creates a fixed roll couple. It is by FAR the most difficult S197 watts link to install, since the axle clamps are how the axle is centered, and they can be placed wherever gives the correct geometry (which make changing the roll center height much more involved than the whiteline or Cortex model, but also more flexible in terms of setup). This link DOES limit the sway bar selection more than the other units, and is why I am going to have to make a custom bar (that and I just don't like any of the rates out there). Mine does make a bit of noise, since the four heim joints have never been replaced, but less noise overall than the standard Koni popping that I also have. I will say that I was very impressed that it survived the roll over of the first car (this is why you don't let friends borrow your race car) without any measurable deformation (bent the axle and destroyed the differential though).
By the way, the watts link does make a difference if you are planning on hitting any FIA curbing. Just don't trail brake on the curbs if you have the same springs, and a 315/30-18, or you will tear chunks out of your undertray (idiot in a GT350R got in my way, and I had to stand on the brakes while crossing the curb to avoid him).