Here is a link to a video presentation given by Josef Bacik, one of the 3 lead developers currently working on Btrfs. This presentation was given at at LinuxCon Brazil 2010. The video lasts about an hour and according to the description provides:
‘A look at the features that currently exist in Btrfs and what features are left to be done. We’ll look at stability and what things testers need to look out for. There will be plenty of benchmarks and use cases for the different features of Btrfs. We will also discuss what testing needs to be done, and how testers can help us developers.’
If you have some questions about the current state of Btrfs, current and future Btrfs development roadmap, benchmarks, etc… you should take some time to watch this video.