As far as I understand, single device and RAID1 is solid, but as soon as you want to do RAID1+0 or RAID5/6 you’re entering dangerous territory with BTRFS.
I had a metadata corruption in metadata raid1c3 (raid1, 3 copies) over 4 disks. It happened after an unplanned power loss during a simulated disk failure replacement. Since manual cleanup of the filesystem metadata (list all files, get IO errors, delete IO errored files), the btrfs kernel driver segfaults in kernel space on any scrub or device replacment attenpt.
Honestly the code of btrfs is a bit scary to read too. I have lost all trust in this filesystem.
Too bad because btrfs has pretty compelling features.