Btrfs still highly recommends a raid1 mode for Metadata, but for data itself, the raid-5 is fine.
I somewhat recall there being a little progress on trying to fix the remaining "write hole" issues, in the past year or two. But in general, I think there's very little pressure to do so because so very many many people run raid-5 for data already & it works great. Getting Metadata off raid1 is low priority, a nice to have.
Still, even with raid1 for metadata and raid5 for data, the kernel still shouts at you about it being EXPERIMENTAL every time you mount such a filesystem. I understand that it's best to err on the side of caution, but that notice does a good job of persisting the idea that btrfs isn't ready for prime-time use.
I use btrfs on most of my Linux systems now (though only one with raid5), except for backup disks and backups volumes: those I intend to keep on ext4 indefinitely.
I have seen a bunch of changes in the past year go by about how scrubbing is prioritized & what capacity it is allocated. On the one hand, unsettling. But also, good to see folks are prodding at this area.
I somewhat recall there being a little progress on trying to fix the remaining "write hole" issues, in the past year or two. But in general, I think there's very little pressure to do so because so very many many people run raid-5 for data already & it works great. Getting Metadata off raid1 is low priority, a nice to have.