So far, so good! Keep in mind I had confirmed from the other MacRumours 2020 iMac memory thread that this should be a safe bet based on the experience of other users.
Here's my detailed response:
I had setup the iMac first with the installed stock memory just to make sure there we no issues and then proceeded to swap in the Crucial sticks once the machine was up and running. I had trouble getting it to boot on my multiple first attempts post-upgrade, but I then reseated the memory and it was fine (I am pretty sure one stick was loose, whoops.)
I had resisted using an Apple Pencil to open the door as I had seen in a video or article, but every other pointy (but not sharp) object within reach seemed to just not quite be thin-enough-yet-strong-enough to open it.
Once you do change the memory the first boot does take an extra 45s-60s where it'll be a black screen, so don't panic!
I haven't run any benchmark software, but it has been holding up well to some of the heavier tasks and games I've thrown at the machine so far. (Cities Skylines is one that will eat up all of memory you can give it by building a very populous town. Smooth like butter.)
Super glad I got it at Prime Day deal. I had a few brands from a few shops queued up/tracked in a spreadsheet and it was the perfect deal at the perfect time – especially with my Mac shipping ahead of schedule. Until then I was leaning towards 2x 32GB for the short term. Shipping wise it worked out well too: the memory ended along with the iMac, on the same UPS delivery. (I had the memory shipped to Canada via US Amazon.com as the Canadian site didn't get the deal.)
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