Btrfs is still in heavy development and still considered "unstable" by Chris Mason, and many important features are still being added, but the dire warnings of data loss are calamity are long since gone, and it has already become the default filesystem for many distributions, and several distributions have declared it "stable" for their purposes.
And while some risk most certainly remains, there's also some risk inherent in disk storage that is mitigated, such that btrfs has been shown to detect and correct data corruption issues that even high-end RAID cards will miss.
So you can expect that there is some point at which Btrfs, even in its in-development status, will be safer for data than traditional "dumb" filesystems like ext4, because the data-preservation features will outweigh any risk of bug-induced data corruption.
So where is that point? Have we passed it already? Or is there some known fault in Btrfs that should be fixed before we trust it?
Or perhaps do you just wait for enough other people to trust it first?