It's a very stabile slalom-foil sail (I have it in 7,2 and 6,0)
-a bit more weight than Phantom Iris RF, but (I think) will last longer
-compared to the PD Foil+ faster, less low wind capacity
-4 camber, very good rotation (on a Slake MDM)
I really like the S2, I use it on a PD FC 78 V2 with 740 and 671/607 Sabfoil.