With a few opportunities to shoot my Z7, plus a look at all of the competitors at PhotoPlus (including the GFX 50R in hand - I'd previously seen a GFX 50S, but not a 50R, and both the Panasonic S1r and the GFX 100S under glass)... I certainly picked the right camera for my use - of course, others' use cases will differ.
The Z7 handles
very nicely - it's nothing like my Fujis, but it is a lot like any other modern Nikon. Still getting used to the Nikon handling a bit, but I've always felt that Fuji and Nikon have the two best control systems...
The build quality feels superb - I completely believe Roger Cicala's teardown (I've never seen him so impressed with any camera's build). The one issue is that it's possible to accidentally open the XQD door while getting the camera out of the bag. I'll probably tape the door a bit in tough conditions (the seal's excellent - I just don't want to accidentally pop it open).
The only other issue I've had is that the shots remaining counter (on the card) isn't completely accurate - it usually indicates fewer shots than it really has (this in NEF plus large/fine JPEG). Many cameras do this, although Nikons tend to be off by more than some others...
Looking at the competitors:
The looks I had at the EOS R I had at PhotoPlus confirmed what I saw at my local camera shop - the body doesn't match the quality of the lenses, and they don't really look like they go together (could there be another body that they didn't finish in time for this release)? The body is a nice size, but feels
much less solid than the Nikon. The lenses are big and heavy (I haven't seen the little 35mm macro), but beautifully built.
The Panasonic looks like it is close to the size of a D850. There was nothing else in the case to compare it to (it was in a separate case quite a ways from the nearest GH5 or G9), so that is a guess, but it is BIG. The prototype looks relatively finished and production-quality, but I don't think anybody's seen one turned on.
I can't see what still specification it could possibly have that would make the size and weight "worth it" - why would you want a camera the size of a D850 that offered no advantage over a D850 (or a 5DIV if you prefer Canon), without the huge advantage of one of the established systems (and it won't have really solid adapters for anything other than a 12 MP crop using Micro 43 lenses) . We already know that it is about the same resolution as a D850 or a Z7, and it can't have much more dynamic range unless it's got 16-bit output (which has never been seen on anything except a few medium format SLRs). It does have some sort of sensor shift that supposedly generates a 168 MP image, which may be useful for certain situations, but all current versions of this technology require absolutely no motion in either camera or subject, limiting use outside of the studio.
I'm still optimistic that Panasonic will do something class-leading in terms of video. There are unconfirmed rumors of raw video floating around, but Panasonic employees in the booth would not talk about any specification other than those that have already been released - they'll confirm 4K, but nothing more. There doesn't seem to be anything special about the initial lenses from any specification I've seen. Of course, it's all been "look but don't touch", and they've been VERY coy about specifications (can't even get a weight out of them), but I would think they'd be talking about anything special, trying to get people to wait for it..
The GFX 50R is much larger than it looks in many pictures. I had imagined a somewhat larger X-E3, and it DOES look like an X-E3, but it's probably twice the size. It's about the size of a D850 according to camerasize, but it actually feels bulkier than that... The 50MP sensor is well known for its image quality (and the prints Fuji had in the booth were very impressive) - but it's really big if that matters to you. It handles very well, but it handles like a big camera - I've only handled a Mamiya 6 or 7 a couple of times, and they were years ago, but it's much more like that than any APS-C Fuji, or even any Leica. I've never used the Fuji "Texas Leicas" that used 120 film, but I suspect they're similar. The only real differences in bulk between the 50R and the 50S are the viewfinder and the "hump" on the back of the 50S. The 50R may actually be larger without the protrusions.
Here's a camerasize comparison between the GFX 50R with the 32-64, the D850 with the 24-70 f2.8, the EOS R with the 24-105 f4, the A7rIII with the 24-105 f4 and the Z7 with the 24-70 f4. Camerasize didn't have the Panasonic yet. The lenses aren't quite fair (the D850 has a faster lens, and the Z7 lacks long-end range compared to the Sony and Canon, while the Fuji has less overall range), but there aren't comparable lenses for all the bodies. Each one is the zoom I'd use to carry around, though (the lighter options for D850 and A7rIII sacrifice too much quality).
http://j.mp/2OixXchSeeing a GFX 100 under glass, it is much larger than either of the GFX 50 models. It's at least the size of a D5 or a 1Dx II, maybe larger. The prototype is clearly a long way from production - the integrated vertical grip doesn't look like it matches the rest of the camera at all. It almost looks like the grip is a 3D printed addition. Maybe it's an odd design decision, and the grip really will have a different finish, but unless that's the case, it looks six months or more from production.