For me, the big potential winner is better Autofocus. The AF on my R5 is already amazing, but I hear people talk about the R6II being better, the R3 better, especially in low light. I am interested in what the R1 will bring to the table and with the first two bullets dedicated to AF, I am hoping there is something there.
The sensor readout speed of 0.8 milliseconds (what I think Craig meant) is outstanding and actually correlates to the 1/1250 = 0.0008 sec or 0.8 millisec syn speed (also great).
The prebuffer of 1 sec. If implemented well, this will be another incredibly welcome feature. The implementation in the M6II is clunky.
Then it sounds like fps will be up to 120 fps continues, 240 burst. I so do not want that. But give me control over selecting my fps up to about 30 fps and that would be very welcome.
Better DR is always welcome, but usually more of a marketing statement. If more than 1/3 of a stop, I will be curious if it is manipulation. I am not sure how much more can be done to get more out of the sensor, but this could be Canon adjusting the image after capture somehow. We'll see.