My first experience with S-Squared was the 30K service. I had them change the fluids to synthetics. Also had shockproof added to the dif. Unfortunately, I noticed shortly after the switch the rear dif. felt like it was catching. I talked to Aaron at the shop about the problem, and he told me to come in right away and get it checked out. They pulled the fluid and apparently shockproof had been added to the rear dif. I guess this is a no-no. They fixed it right away and then flushed it again the next week. I have zero complaints. Everyone makes mistakes and they were pleasant and speedy to fix.
I give them 2 snaps in a Z formation.