No, I am not buying X3 again unless I know it will be a better port than X2 was. Do you have any initial performance impressions you could give?
X2 worked fine on my machine. (Joystick support was problematic; but the port itself was stable and had decent performance)
As for your question, the Beta isn't out yet.
... And LGP requested that people, at least in the beginning, will refrain from posting performance numbers. (I assume that the initial builds will be riddled with debug print-outs and will not be optimized)