I've not been super happy with my Nikon cameras for a while now. Both Sony and Fuji seem to be pulling ahead technologically with their mirrorless systems. I recently had to send in my Nikon D5 and D810 cameras for repair, so I used that as an excuse to rent the Fuji X-T2, the 18-55 lens, the 23mm 1.4, the 56mm 1.2, and the EF-X500 flash.
First the bad:
Battery life. It stinks. Full charge to completely empty in about 90 minutes (about 330 shots). I didn't rent any extra batteries, so this made it even worse. My D5 will last a week even with heavy use.
Focus. Compared to the Nikon D5 (arguably the best focusing camera out right now), the focus is slow, and the continuous focus is strangely bad. The camera can't seem to lock focus even on objects that aren't moving. I was attempting to make a portrait of someone with continuous focus on, and it simply couldn't focus on her even though the camera locked on to her face.
Flash. Lastly, the flash is just not good. Using TTL, it could not get a good exposure. My Nikon speedlights are always spot on. The Fuji needed constant overriding in order to get a balanced exposure.
Now to the good:
Size. It's small and light. I love carrying this thing around instead of my go-to event photography kit -- Nikon D5, 24-70, and SB 910 (often with some sort of diffusion.)
Mirrorless. I love the ability to see the image before I even hit the button. I'm a fully manual shooter, so seeing the image in the viewfinder is huge. I found that using any of the auto modes simply created images that were too dark or too blue. It's a huge time savings, as I don't have to tweak each image in post to make it perfect. I get it perfect in camera now. In fact, I shot in JPEG and RAW just in case, but I only ever used the JPEGs. And it's silent. I often find myself not shooting in quiet situations, because I don't want to disturb others. Not a worry with the Fuji.
Image quality. The Fuji JPEGs were superior to the default settings in Lightroom and Capture One. The noise control is surprisingly great. Compared to my Nikon D5, it's about the same when viewing images full size on a 27" screen. I reduced the noise reduction in the camera to -4, so the JPEGs actually came out better detailed and with less noise at the same ISO.
Workflow. Being able to share an image immediately is a bonus. Before, I'd have to wait until I got home in front of my computer before sharing any images. I had a client ask me if she could have one of the images, so she could immediately share on Facebook. I had to tell her my $6500 top-of-the-line Nikon can't do that.
In the end, I really enjoyed my time with the camera. It's a different way of shooting, but one that is great for events. With my Nikons, I'd shoot in RAW, import to Capture One, wait as the previews are rendered, edit images (because there's still some guessing when picking exposure during events and auto white balance never seems to be accurate), then export as JPEGs. With the Fuji, I get everything dialed in before pressing the shutter button and rarely tweak an image in post. I'd guess over 90% of the 2000 images I took this week were delivered straight from the camera. The rest were slightly adjusted and that was just some cropping. It's a huge time savings.
I'm selling my Nikon D5, D7200, and a few lenses that I just don't use very often and can live without. I'm keeping my D810 (until the D850 is released) for commercial shoots. For events, I'm picking up the Fuji X-T2, X-T20 (as a backup), 23 mm f/1.4, 10-24mm, 50-140mm, 18-55mm, the Godox TT685F flash, battery grip, and four extra batteries. Probably grab the 56mm f/1.2 at some point too.