I had a reasonably good time with it. I had issues with btrfs, which is why I moved off it and went to Fedora IoT for pretty much the same benefits.
For me, btrfs caused multiple drive corruptions because of unexpected power offs, and I didn't feel like trying to fix that on the fly - it might have been drives that were incompatible with CoW because of firmware "optimisations" that break if a write isn't completed prior to power off.
In general, outside of that, it was pretty solid. I didn't find much use for the orchestration/setup tooling they include, and I found their documentation pretty sporadic unfortunately. Fedora IoT has the advantage of basically being silverblue, with rpm-ostree, so it's easy to find people using it and discussing it.
It'd be worth checking out Borg as an alternative to rsync. Borg will handle snapshotting, and automatically de-dupe on a block-by-block basis.
I use it for all of my remote backups, and it provides a lot of quality of life stuff that rsync isn't going to handle.