Why should it matter? It's an extremely niche technology that's only interesting to some home users. I see no reasons why other users should care about a RAID level they're not interested in.
(I don't use btrfs or any other COW filesystem because of significantly worse performance with some kinds of workloads, but it has nothing to do with maturity of any of them.)
(I don't use btrfs or any other COW filesystem because of significantly worse performance with some kinds of workloads, but it has nothing to do with maturity of any of them.)