This comes from frequent contributor Mike Craven:
I just finished installing the JCW suspension kit (along with an Alta 22mm rear sway bar) on my 2005 MCS today. The install was totally doable but quite time consuming. It took me about 5 hours to install the kit from start to finish – and I did it all by myself too. However, after driving it, I found that it was totally worth the time and the money I spent on it. The car handles great now! It’s just what I was looking for.
[ JCW Suspension Instructions ] Offical MINI PDF
I didn’t want something too stiff as I use my MCS as a daily driver. However, I wanted a suspension kit that would make the car more stable at speed and help make the new engine mods I just did (19% pulley, GIAC, JCW Injectors, Milltek exhaust, and JCW CAI) get the power to the ground. The JCW suspension kit does exactly that. While I am impressed generally, it would be nice if they would have sent the new struts fully assembled instead of making us go through all of the work of disassembling our existing struts just to use the old dust boots, etc.).
Also, just as an FYI, the JCW suspension (at least the struts) are made by Delphi in the U.K. They are the same company that made the OEM/Factory struts that I took off of the car.