Another update from me and I hope you guys don't mind my snippets and also that I haven't processed any of my shots to post here, YET :
Currently I have my EOS R mounted on an EF 500mm F/4L II + 2x III on a Gitzo Fluid Head gimbal on a Skimmer base on the sill of an open window at home. This set up, poking through a military camouflage curtain, and overlooking my wildlife garden, enables me to come and go to shoot in comfort. It is currently as dull as dishwater outside although the light is possibly slowly improving and it's still very windy.
As usual I am shooting in Manual-mode with Auto ISO with a 3200 upper limit.
AF actions quickly and smoothly and with less focus hunting than with D-SLR bodies, or so it seems. The EVF viewfinder is, as many people have already reported, extremely comfortable (much better than the EOS M5) and being able to see an exposure lighten or darken is very helpful together with the option of a visible histogram with two display size options. Shooting wildlife I never seem to have time to leave the viewfinder as you have to with a D-SLR to check the histogram and because of that I have tended to ignore its very existence until post-processing.
You have to play around quite a lot with the Menu settings to set the camera up how you most like it and then be prepared to change some as you move onwards and upwards. This is especially so if you also have an EOS D-SLR.
I am finding that what Canon call the 'Quick control dial' (around the Mode button) a bit too recessed which makes it easier to unintentionally action the Multi-Function Bar. But I think, and hope, I'll get used to it even if I have to disable the touch Bar (which can be slow to respond anyway). We'll see < I'm still learning what customisation will suit me best.
As it's windy I decided to test the Drive fps on some moving leafy branches. Because I am now used to the 14fps of my 1DX-2, my expectations of slooow fps rates on the R have been very poor. Furthermore, the handbook states that fps will suffer when shooting Dual Pixel RAW (which is the only option I am interested in selecting) and also suffer in AF SERVO to the extent that it might only be 3 fps. However, all 8 of the moving leaf images I continuously shot were in focus and the 13 which I just shot of a perched Goldfinch moving his head and twisting his body captured enough bird body positions to give me some keepers and one image which, subject to sharpness, I hope to keep. I was unexpectedly and pleasantly surprised by that but I'll see what future scenarios can deliver. All images look particularly clean on the LCD and with fresh natural colours - Bright without being over saturated. I have Picture Style set to Neutral and RAW to its highest quality.
Incidentally the AF Focus Point turns blue instead of green when in AF SERVO - A nice touch < I wondered and was confused why it was sometimes blue! I have my (adjacent to AF-ON) star button customised to toggle ONE SHOT / AF SERVO.
I'll have to wait for my Control Ring Adapter to arrive before I can settle my customised settings so that they match whether I'm shooting on either an EF or RF lens. I have no plans to add another RF lens to my EOS arsenal.
Will I be shooting more with the R and the 1DX-2? < No! I'll shoot with whichever is best for the target.
Will I upgrade my R to a higher-end R when released? < Not if it doesn't have an articulated screen. I have always missed the articulated screen of my 70D.
Will I upgrade my 1DX-2 to a mirrorless EOS equivalent if released? < That depends on several factors and cost might be one of them but I am liking things about mirrorless technology.
Although I am talking about myself in these posts, I hope that readers can find useful information for themselves in them.