That file is a bit old, it hasn't been updated since 2009 - While it might not be production-ready, it's not as bad as it does sound (for example, the disk format is finalized, and shouldn't get any changes in the future).
As for the distros, I think none of the big ones default to it yet, but it's definitely a first-class citizen in OpenSUSE (and should be the default fs in OpenSUSE 13.2, according to the official plains).
The wiki hasn't been updated for the last few kernel versions either. I think the only place to get good information right now is the IRC channel, #btrfs on freenode. webchat.freenode.net/?channels=%23btrfs
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux....
"Btrfs is under heavy development, and is not suitable for any uses other than benchmarking and review. The Btrfs disk format is not yet finalized."
That said, I know lots of people use it day-to-day just fine. I think some distros even default to it these days.