I have the Sachs organic clutch combined with a lightweight SMF, in overall really satisfied with it! My clutch was still ok but the DMF was rattling like crazy so had everything replaced including release bearing. The main reason I decided to go with a SMF setup was reliability as I drive the car pretty hard and will be occasional trackdays in the future. My tuner also recommended this setup over a DMF.
The main benefits of having the SMF are the mentioned reliability (should be bulletproof no matter how you drive it), and a slightly improved throttle response, easier to rev match and heel-toe too thanks to that.
You will notice some flywheel chatter mainly when engine braking or at idle, other than that I can't really think of any downsides. The Sachs kit I have is balanced together so vibrations are kept to a minimum, even when running upgraded engine/gearbox mounts like I am. The clutch is really easy around town too, biting point is somewhat different but nothing you won't get used to. From what I've read the engagement issues mentioned above has to do with a worn input shaft bearing on the gearbox, luckily I haven't experienced that issue so far.