The kernel hotfix from a few days ago to break an infinite loop regression:
https://www.phoronix.com/scan.php?page=news_item&px=Linux-5....
And the announcement last year of officially giving up on RAID5/6 support, after not discouraging the totally dangerous feature for years:
https://www.phoronix.com/scan.php?page=news_item&px=Btrfs-Wa...
I would love to have options besides ZFS for check-summing and snapshots, but BTRFS isn't for people who care about their data.