Just installed Fedora 18 on physical hardware and selected btrfs. Did the following on a 1TB volume:
dd if=/dev/zero of=test bs=1M count=6144
rm -rf test
The rm process went to 90%+ CPU and took 2 minutes to delete the 6GB file. Write performance for dd was OK at roughly 150MB/sec.
After observing rms performance I wiped the box and re-installed using LVM and ext4 and we are back to normal rm times.
I don’t know if the btrfs file system caused my computer to freeze but I had several general protection faults while I had the btrfs setup running.