I think this camera will be a game changer for Fuji, as the D3 was for Nikon.
It looks very similar to the X-T1, but is in reality very different. There are many changes, some large and some subtle, and I am sure I have still not found them all.
My immediate impressions of the image quality of the new sensor are that it is excellent, but I need to do more testing.
The first thing I noticed is that the is much more responsive. The AF is fast and precise, something where the X-T1 was weak. With AFC the viewfinder snaps straight into focus, with none of the pulsing which made it unusable for me in the X-T1.
The viewfinder is even better than the previous model, which was always a strength. More importantly, the refresh rate is much faster, even in standard mode (I have not yet tried Boost mode, as this works best with the grip which has not yet arrived for me). Tracking moving objects at 8fps in AFC is now easy - in the case of the X-T1, I felt I was always playing catch-up.
Fuji has listened to the complaints about the AFL set-up, and it is now possible to decouple AF from the shutter button and use proper, Nikon style, back button focussing. This can be switched from the AFL button to any of the eight function buttons. I have set it to the AEL button as recommended by the Fuji rep, as it suits my hand better.
These changes mean that I now feel comfortable with using the camera for action and wildlife, which was not the case with the X-T1. Now all I want is some more long lenses from Fuji.
The push central button and turn dial system for ISO (and to take the shutter speed button out of A) has gone, and has been replaced by a press to unlock and press to lock button. So you can have locked down ISO or shutter speed dials, or have them click turn. This is a big improvement as far as I am concerned.
Focus point selection is by a joystick, which is a huge improvement on the D-Pad. The buttons on the D-Pad have reverted to being function buttons.
There is a two button press to format the sd card, so no need to go into the menu for this.
There are two sd slots, one for a UHS II card and one for a UHS I card. The UHS II cards I have (Lexar 300mb/s) are dramatically faster than my fastest UHS I cards, and I recommend UHS II to get the full benefit of the extra capability of the camera.
There is a new centre weighted metering mode, to add to spot, matrix and average. Unfortunately, in average mode, the control is awkward to move. As I never use average, this is not a problem for me.
The shutter button release is threaded for a standard cable release.
The battery can be charged in camera through a USB cable plugged into a computer.
The menus have been significantly rearranged and are now much more logical.
All in all, I would say that Fuji have responded to user comments, and have changed what needed to be changed while mostly not changing what was fine.
The camera is well thought out and is a pleasure to use.