Christian Fletcher published few samples taken with the Fuji X-Pro1 camera. The image above was taken at ISO 6400 (click on image for full resolution). Christian will be posting new images over the next few days, so bookmark his website.
I guess Fuji was serious when they said about the X-Pro1 that "resolution and low noise will surpass rival 35mm full size sensor".
The official X-Pro1 website doesn't include any sample images taken above ISO 1600.