but is that an inherent sensor improvement, or just better on-camera noise filtering? dpreview might say (and if it's just better on-camera filtering, I can beat anything that a camera offers onboard with the noise removal plugins I wrote).

Last time I looked at dpreview, the camera sensors varied almost none at all (aside from size) and it was all about the onboard image processing filters that distinguished one camera from another. If the fuji really does have that much better a sensor, it's definitely worth knowing about. ISO 12800? madness!