Thanks for the great report. I like most things about this camera except for the backwards focus choices in the menus. The focus choices are like the ones I had in my old EOS 7D. Why didn't they make the focusing menu like the 7D II or the new 5D series. Also, 2 weeks before the release of this camera the Canon Learning Center had a hands on preview of this new camera and I got to play with one and use some of the new lenses too. They made a big deal out of the eye recognition. But when I tried it, it failed 8 out of 10 times. I think that they were making a big deal out of nothing. The other thing I didn't like was that they say it has so many fps burst but when it's used in AI-Servo mode tracking a subject it falls off dramatically. Maybe if they had used the newer focus menu choices like in the 7D II or 5D IV it would do better.

Well, there is definitely a learning curve compared to my previous Canons (starting with a T3i) and up to my current one, a 5DIV.
I was concerned about a "toy camera" look and feel. Nope. Even though it is noticeably smaller compared to the 5DIV it has the same well built, well finished look. I know, it's not as stoutly built or as well sealed, but the look and finish are fine. It fits well in my hand (which are on the large side) and all the controls are easily accessible.
There are fewer buttons. No "Mode" dial, for example. Instead, there is a Mode button in the center of the rear control wheel. Press the Mode button and you can use either control wheel or the touch screen to make your choice. The Mode is always shown on the top display even when the camera is off. Take the battery out and it goes away. Obviously it uses some power even when the camera is off. Canon recommends removing the battery whenever the camera is not in use for any period of time. Even overnight I would say.
A quirk that I noticed: There are 2 control wheels. On top, one towards the front, one towards the rear. In Av Mode the front wheel sets aperture and the rear wheel does nothing. In Manual Mode the REAR wheel sets aperture and the front wheel sets exposure. May be able to re-program that. Haven't checked.
Most of the control functions operate differently then on previous Canons. For example, on the 5DIV there is a dedicated ISO button. Push it and then use the control wheel to change ISO. On the EOS R you push the M-Fn button. This brings up a display with 5 functions to select from. You use the rear control wheel to select the function to change and the front wheel to make the change. Sounds inconvenient but after using it a few times it doesn't seem to be. Not to me, anyway.
Most all the buttons, wheels, and bars are customize able. Since I don't shoot video I use the Video button to instantly re-center the focus point/points. The * button I use to shift between One Shot and Al Servo. The M-Fn bar I have set to toggle between Auto ISO and 100 ISO. It has a safety feature to prevent accidental switching since all it requires is a touch. The bar doesn't actually move. It's just a touch sensor like a touch screen.
The menu is very similar to previous Canons and is displayed with a push of the Menu button, just like on previous models.
The LCD display comes on as soon as you turn on the power and stays on until:
1) The camera goes to sleep.
2) You reverse the screen.
3) You put your eye, or anything else, close to the EVF.
4) You disable it in the menu, leaving you just the EVF.
While the movable LCD screen certainly requires some care in using it, it doesn't seem fragile.
The new control ring on the RF lenses and lens adapter allows ISO to be changed by depressing the shutter release halfway while rotating the ring. Or, you can push the AF ON button located on the rear and rotate the ring.
The EOS R with the RF 24-105 weighs about 6 oz less then my 5DIV with EF 24-105 L IS (Earlier version, not the MkII lens).
Contrary to what some have claimed, Canon has not prevented the use of non-Canon batteries. The camera can use either LP-E6 or LP-E6N batteries interchangeably. I have 2 LP-E6 batteries that are at least 3-4 yrs old. One is a Watson and the other a Power2000. Both work just fine in the EOS R and display all the same data as the Canon LP-E6N batteries do. Same as in my 5DIV. No problems at all.
So far, even though there are differences, I don't find anything about the camera to be clunky or awkward. It will definitely take some practice to be comfortable with but I think I will find it to be quite user-friendly.

Attached is a jpeg I shot while sitting on the floor playing with the camera. I just set the camera on full auto to see what it would do in relatively low light. RF 24-105 lens. f/4.5, 125th/sec, ISO 8000. Focus point was the book titled "The Sword And The Shield".
(I know, I need to dust! My job since I retired, as my wife occasionally reminds me.)