Ok, Here is my review and opinion of the new Bridgestone S20's...
I started the day on saturday at 30/30 psi cold temp. That was ok at first when not beginning to really turn it on yet. about the 3rd session right when the temp was getting HOT, I had my first slip of the tire. Coming out of a left hander as getting on the throttle the tire slightly slid out on me but was very smooth and predictable (almost like it meant to do that). It did not even spook me because it was very forgiving. I got back into the pit and the hot pressure was around 38 (TOO HIGH!!!) After adjusting the pressure I went back out and a couple sessions later I had the same thing happen in another left hander. The slide was not spooky at all but just letting you know too be careful or she might let go next time
... Well at this point I had in my head that I did not like the tires at all because NEVER did a Q2 do this to me. But I decided to hold off on my final decision and I figured the sliding of the rear was definately due to it being 95 degrees and not finding a good PSI for the tire.
Now for sunday.... This was a MUCH better day as far as traction goes. The 3rd session right about the time the heat got to it's peak I set my best lap of 1:06.7... I was feeling a lot better with the tire and it was not sliding on me like the day before. I was able to get it do a good pressure that made me comfortable pushing it hard. For the remainder of the day I was running consistant 1:07 laps in the Advanced group. There were a couple of time were I could feel the tire about to slide or just doing what it needed to do to keep me from crashing.
At the end of the day, I had changed my mind about the tires. I realized that I was able to run a respectablt Advanced pace at a track I have never been to before on a tire that I have never run before (and this is a STREET tire). Because of this, I realized the tire actually did it's job well. Would I choose a set of the S20's over the Q2 if both were sitting right in front of me? No, but given the S20 is currently $50 cheaper than Q2's, I would definately buy and run the S20's again. (actually bought 2 sets and will be running them at my next track day)
Overall, the Q2 still holds the #1 spot to me but the S20 performed VERY WELL and would not have any trouble recommending them. Obviously I cannot comment on mileage or treadwear as I ran about 250 miles on the track this weekend and the back tire is NONEXISTANT, front tire looks great tho.
Hope this helps.....