I could ride it very shortly with a 8m rpm. I can´t say much about it yet, because the wind dropped too fast.
What I can say is, that it seems to love tight turns. And that it needs quite a bit more wind than the Celeritas. I didn´t have any more fun in the dying wind with the 5´4 Screamer, but when I changed to the 5´8 Celeritas it was fine again for a while.
Regarding upwind-performance, I think the Celeritas is just really hard to beat. So, I don´t think, the Screamer can do that better.
It may ride like a bigger board but to me it still felt like a small board. The difference in lowend compared to the Celeritas is quite big. So I would never sell all other boards in favor of the Screamer. I am considering to get the Screamer instead of my Tyrant. But I don´t really know yet.
Here you can see them side by side (I rode both boards strapless):