Tried the EOS R, when I visited one of my local bricks and mortar photography stores today (I walked to the nearby store in my break). Below are my initial impressions:
The camera felt very solid in the hand. Nice grip... slightly deeper feeling than my 80D. For my hands, both are extremely comfortable.
With the RF 24-105mm f/4 lens, it felt slightly heavier than I expected it to be. For some reason it felt somewhat heavier and more front heavy than my 80D with EF-S 15-85mm lens, but this may just be because I am used to the exact ergonomics of my 80D and 15-85mm.
The AF worked well - that predictable smooth, definitive and accurate DPAF. Similar in speed and smoothness to my 80D in live view, or my Canon EOS M5, though the EOS R was possibly just a tad faster. As they only had the RF 24-105mm to test/ play with, I could not really test its ability to focus in low light / low contrast, but again it felt similar to what my 80D could achieve with the 15-85mm lens. I would love to test this with faster glass, in the future.
The 24-105mm f/4 lens worked well, the focal length range (from 24mm-105mm in "FF" format is useful). The zoom ring was fairly stiff (it was obviously a very new lens, store said they only just received it in). The focus ring lighter / smoother, and the control ring nicely damped, with 'clicks'. Great ergonomics on the lens too, though as I mentioned it all felt a bit more front weighted than my 80D and 15-85mm.
The EOS R's electronic view finder (EVF) is great. Very faithful and natural colours. When I viewed the scene directly and then through the viewfinder, it was VERY accurate. Impressive. Plus a very smooth look and feeling in the EVF, much less digital feeling than the M5 (which I feel is not too bad). Naturally the M5's EVF is smaller. The EOS R's EVF was also notably faster in response to changes between light / bright and dark than any other EVF I have used. That is, when pointing to the store lights, or the window outside, as opposed to a corner of the behind the bench counter / cupboard.
I didn't spend much time customising the camera to my settings, but yes, I could see how it would take a bit of time getting used to the mFn touch bar and the AF button was placed slightly to the right compared to other recent Canon DSLR's I have used. These two factors are not poor ergonomics, imho - but just different. I reserve my final judgement about the mFn touch until I would have used one for an extended period (at least a week using it extensively).
I do feel Canon lost a lot of valuable real estate having a reasonably sized round dial just to turn the EOS R off/on. Would have preferred a mode dial there, with a 'off/on' toggle/switch around it (as several DSLRs have) to be honest. The rear screen's colour and clarity reminded me of my EOS M5's rear screen (which is very very good), and my 80D which is very good. I am glad the EOS R's screen fully articulates (which my M5's doesn't). The EOS R's screen feels very sturdy.
My initial feeling about the other buttons, is they are good to great. Though my first use of the camera made me feel that I am not a huge fan of the smaller round four way button / combination configuration at the rear (to the right of the screen). I would much have preferred a round wheel (like the 5D / 7D series) - perhaps a bit smaller, say 80D's size. But the 80D's is somewhat spongy. However again, this is an ergonomic aspect one can (possibly) get used to the change and/or see benefits in some other ways.
The battery door felt very solid (they had to try a few batteries - the first one they used (taken from the was staff cupboard) was flat. So they handed me another (again, 'staff available') battery- which I swapped the first with. So all these aspects speak to quality and durability. The overall EOS R camera and 24-105mm lens combination felt very tight / well matched together, as in - I would not hesitate to take it into any terrain I would take my 7D and L lenses into.
I hope these initial impressions and experiences of mine are helpful reading to some here on CR. I am glad to have had the chance today to have a relaxed play with Canon's latest mirrorless (and first FF mirrorless) with a dedicated RF mount lens. To be honest, I feel that I would like to see a few more FF mirrorless models - and then make a choice between them, rather than jump into the first model. Particularly a higher spec FF mirrorless, with some additional "semi-pro" features would go a long way of encouraging me to make the step to FF Mirrorless.
Regards
PJ