I gotta say, I played a lot of tennis this weekend. The more time I spend with the 99S, the more I like it. My serves are as good as they've been since I played with the K90. I can hit the corners, spin is good, surprisingly, my kick serves aren't as kicky as they were, but time will solve that.
I played with my usual complement of 5.0s last night, and I held serve pretty easily. My slice out to the ad court completely confounded one of the 5.0s to the point that he kept saying "I've missed 100% of those damn serves". After the match, he said that the ball basically shot away from him. BTW, he's one of the 5.0s who plays with the 99S as well.
From the backcourt, I won every rally with this guy again to his chagrin. At net, I did miss a few, but this frame feels so solid.
I have 7 sets of play on a set of Wilson Spin Cycle which is more than acceptable to me; it is though near breaking. The frame does give me more spin, obviously, but I prefer to think of it not as a game changer, but more as an the open pattern that I've always been wanting!
Everyone who plays with it comments one way or the other, but all feel it is supremely comfortable. The 5.0 I mentioned says it has cured his sore arm which he got from a Babolat Aero Pro Drive.
Wilson Steam 99S poly Luxilon 4G 1.25 @ 45