I think you are in need of some longer term reviews of the R1, particularly of those that owned the R3. I cannot help you there.

The early impressions I am seeing is that the R3 is holding its own against the R1. It seems that Canon has emphasized readout speed and the R1 is at 2.7 vs 4.8 milliseconds for the R3. Both are incredibly fast, but part of my thought process on buying the R1 is that this would also help with AF speed. Add in the Digic accelerator and I think there is reason to believe that the R1 will outperform the R3 in certain circumstances.

While I know not everyone likes "Youtube" reviews and some are certainly comically bad, I think Whistling Wings has done a nice job. BYU Photo is also pushing out content. Some of his videos are long, but they are bookmarked so you can jump to sections pretty easily. But, the quick summary, both of those guys have jumped to the R1 and are finding better AF/AF Tracking.

My own experience is a bit odd. I think the 45 MPs of the R5 helps as it seems to find a birds eye better in some scenarios. Yet, the R1...yeah, no doubt it is quicker than the R5. No doubt. Shots where the blue box wasn't even on the bird yet for the first image and I look and the shot is in focus. Is the R1 perfect, no. But where my R5 AF would almost never stay on the bird as it jumped from one point on my branch to another, the R1 is giving me usable photos about 50% of the time.

All that said, the R3 does really seem to hold up. Great camera. As Ron from Whistling Wings says in the finale of the R1 Impressions, R1, R5 II...great cameras. Can't go wrong. Then he included the R3 in a great camera you can't go wrong with.