Where'd you hear that from? TMZ?! But yes, the rumors are true, I have made the official switch to the Steam 99S. The crazy spin I could put on the ball was just too tempting.
With regards to the stiffness, I haven't really notice any arm pains. I think it might be due to the fact that I do use softer polys like a TCS and also that I don't string it up too tight. Even with the 16x15 pattern, I usually keep it around 55-58 lb range.
Spin with the 99S isn't comparable to any regular string patterned racquet, not even with the Aero Pro Drive, in my opinion. I love that racquet, but it doesn't put the crazy, last-second-drop-in-right-at-the-baseline spin that the 99S does.
I'm going to be experimenting with some customization very soon. I want to lower the swingweight just a tad, to the mid to low 320s. We'll see how that goes. But I'm very excited to start customizing the 99S!