Oracle has provided  a link to a webcast (registration required) on the state of Btrfs given,  by lead Btrfs developer Chris Mason.  Here is an excerpt from the webcast description:

‘Join Chris Mason, Director of Software Development at Oracle, the principal author of Btrfs flie system, and our own resident Linux kernel guru, as he discusses the development, features, benefits of the “Btrfs” file system (pronounced “Butter F S”, “B-tree F S”) in Linux.’

The video lasts about 1 hour and provides a very good overview of the current state of the file system, some of the pros and cons of Btrfs under various workloads, some of the features that have been implemented thus far, as well as some of the tools and features that a slated for future releases.