I used this tire at the track. Prior to this tire, I ran the Dunlop Q2 which I found to be an amazing tire. I wanted to try something different since Dunlop's prices went up but was hesitant to try the S20 since it's supposed to be a step "down" from the B'stone 003RS which I tried (at the track) and hated, but I gave it a shot after hearing some good reviews from track riders whose opinions I trust.
I was very impressed with this tire. The rear was stable and gripped well - no traction problems at all. The front provided good feedback with no slippage. I was concerned about flickability since I was used to the Q2 with such a sharp profile compared to the S20, but tried it out with no suspension changes at all and was pleased.
My only complaint, and the reason I gave this tire 4 stars, is that it did not wear well for me. Granted I was at a track that is known to eat up tires, the Dunlop Q2 actually lasts me longer (after some minor suspension tweaks - the S20 may last just as long after a proper suspension setup). I got 2 days out of the rear.
I think these are great tires for street use if you actually need the performance that these provide...which the vast majority of street riders do not.