Btrfs hands on: My first experiments with a new Linux file system
Btrfs is a new file system for Linux, one that is still very much in development. Although I wouldn't exactly describe it as "experimental" any more, it is, as stated in the Wiki at kernel.org, "a fast-moving target".
It has also been said publicly that the basic format and structure of the filesystem should now be stable; it would only be changed in the future if some overriding reason or need is found.
The point of all this should be clear — it is still very early days, and it is not recommended to use btrfs in critical systems of any kind.
I leave it to the reader to decide how critical their systems are; for my own purposes, I will be using btrfs on several systems that I use as testbeds, some of which I carry with me and use for normal work on a daily basis, so it will get a "real" test, but I will not be using it on the primary systems that my partner and I use for home/work/business activities.