If 6400 is like Sony 4000 I really can't see how the XT1 is the equal of the Sony in low light as I can and do shoot at any ISO up to and including 25,600 so the Fuji files would need pushing post capture. I do wonder why the Fuji stick at 6400 when even my GX7 goes to 25,600 and the pictures are useable depending upon the scene and how much noise reduction I want to apply. It would be interesting to shoot an A7 and a Fuji side by side and see what the Fuji files look like when pushed to match, there may not be too great a real world difference.
Anyway, as I said, the relatively low upper ISO limit may not be a deal breaker. I'm just thinking about replacing MFT as I can't see Panasonic adding the options I want... auto ISO in manual exposure mode and constant preview.
Thanks for all the info.