I don't really have any deep insight into the status of Btrfs. A few years ago I was playing around with my Raspberry Pi and it required me to build the newest kernel just to work--I also remember hearing they wouldn't take bug reports until you were using bleeding edge tools. Not very comforting if you were looking to roll out into production.

On the flip-side, Synology just rolled out Btrfs in and update and I'm pretty sure it's the default partition type going forward. They don't expose all the fancy features like dedup, but the fact it's default shows some confidence.

So it sounds like it's being actively developed and getting closer to being trustworthy.