We tried Btrfs for the first time in 2011 shortly after Fedora announced their decision to use Btrfs by default.
Later it was announced that this decision was reconsidered.

Btrfs is still experimental and we were much surprised to see the impatience to use such unstable file system.

We started the experiment by formatting 700 GB hard disk with Btrfs and extracting archived rsnapshot tree with ~12,000,000 files and many hardlinks. That's pretty much where it stopped hours later when Linux-3.0 (x86_64) crashed in add_inode_ref+0x2f3/0x385 [btrfs] call.

RIP  [<ffffffffa016b008>] btrfs_add_link+0x120/0x178 [btrfs]

File system become inconsistent. After reboot mount was not able to return from the call ‒ it was waiting forever while blocking other operations. The whole system was affected by this incident.
btrfsck didn't find anything and btrfs partition was erased less than 24 hours since experiment has begun.

However promising Btrfs looks like it's still not usable at least with Linux-3.0.

Testing was conducted on Debian x86_64 GNU/Linux_3.0