BTRFS performance seems to be not so measurable as regressions, kernel mods and other kernel related stuff seems to be pushing it back most of the time.
Don't take me wrong, Phoronix benchmarks rock, but we have to wait at least one year more.
I ended up choosing EXT4 for "stability" -there are obscure/hidden transaction errors- and choosing Debian because it seems to run faster in this system/distro -perhaps for its lack of compiler optimizations- Even with experimental branch Linux 2.6.38.
BTRFS is not so good with databases at this time, which is a must (also for hobbyist desktops) when you think seriously of it. But I must confess the only sad thing about EXT4 is its lack of a compress option.
Compress is the real must when processors become more powerful and disks keep quite a constant transfer rate. On-The-Fly decompression tends to make things snappier as shown by Reiser4 some years ago.