I went into my local camera shop and they had a Df in. I had a play with it and had an SD card on me, so was allowed to shoot some photos in RAW mode to take home and process / review the files.
first impressions - camera looks great, feels quite light and not as compact as expected. It handles really well, dials feel nice, great shutter noise and feel. It was simply a pleasure to shoot on. LCD at the back is nice and big / crisp to look at.
RAW files - had a play with the RAW files in lightroom 5.3. very impressive. I was testing ISO 3200, 6400, 12800 out mainly and I have to say the noise was pretty good at 12800, definitely usable files.
I'm tempted to buy one to replace my D700,
only worries are the AF system (from the D610) and the 1/4000th shutter speed limit. sometimes use 1/8000 on a really bright sunny day (rarely tho)
I am trying to decide between a new Df and a used D4. also would buy it NEW.
Df looks cooler, smaller, less intimidating to others.
D4 has the superior autofocus system, but bigger / bulkier. also higher FPS and video. Price wise used D4 vs new Df, not much in it.