I can't say that I'm in love with the distribution of mass, but the Graphene S does player very well. You're right about the flex: it's soft without being too mushy/flexy. I found it to be very comfortable.
The S and the Rev Pro are my favorites in the Graphene Prestige Series.
Prince TeXtreme Tour 95
PTR Certified Pro / USRSA Certified MRT / Team Prince