It's generally fine if you stay on the happy path. It will work for 99% of people. But if you fall off that happy path, bad things might happen and nobody is surprised. In my personal experience, nobody associated with the project seems to trust a btrfs filesystem that fell off the happy path, and they strongly recommend you delete it and start from scratch. I was horrified to discover that they don't trust fsck to actually fix a btrfs filesystem into a canonical state.

BCacheFS had the massive advantage that it knew it was experimental and embraced it. It took measures to keep data integrity despite the chaos, generally seems to be a better design and has a more trustworthy fsck.

It's not that I'd trust BCacheFS, it's still not quite there (even ignoring project management issues). But my trust for Btrfs is just so much lower.