Comparing a D800 to an XE-2 should be like comparing apples to oranges. 36MP Full-Frame DSLR compared to 16MP APS-C mirror-less ...
I have been using the Fuji XE-2 for a couple of months now. I bought it to replace my 'walk about' compact camera which was a Sony X100 and with the idea that I might use it as my travel camera when flying abroad.
I didn't expect the quality of the images to compete with my D800, I have the 'holy trinity' of Nikon glass (14-24, 24-70, 70-200 @ f2.8) and the detail within the 36MP RAW files can be exceptional. The Fuji and 14mm f2.8 weighs about the same as the Nikon 24-70 on it's own! It makes my D800 feel like a tank, never mind how it would have made my D3 feel!
I'll post some example images in this post, but in my opinion the Fuji stands up against the D800. So much so that I have pretty much not used my DSLR since owning the Fuji.
I use the D800 for macro shots because I have a macro lens for it and that is about it... I am on the fence about switching entirely over to Fuji!
I expect to keep both systems for now, not due to the quality of the images but there are advantages and disadvantages of both:
- D800 has better, faster focus
- D800 has better battery life
- I have wider selection of accessories for the D800
Fuji may announce a full-frame mirror-less camera at some point. I would be interested and wouldn't want to build up a large set of APS-C compatible lenses and then need to replace..