http://blog.helixoide.com/blog/2013/04/09/converting-from-ext4-to-btrfs-on-fedora/

When you run the dracut step to recreate the initramfs image you can check for the correct module using:

[root@pc01 boot]# cd /boot
[root@pc01 boot]# zcat initramfs-`uname -r`.img | cpio -it| grep -i btrfs
usr/sbin/btrfsck
usr/sbin/btrfs
usr/sbin/btrfs-zero-log
usr/lib/udev/rules.d/64-btrfs.rules
usr/lib/modules/3.12.8-300.fc20.x86_64/kernel/fs/btrfs
usr/lib/modules/3.12.8-300.fc20.x86_64/kernel/fs/btrfs/btrfs.ko
54300 blocks

http://flakrat.blogspot.com.au/2012/06/howto-converting-ext4-to-btrfs-in.html

Still not sure about whether you can convert /boot ext4 to btrfs... decided against it after looking here http://docs.fedoraproject.org/en-US/Fedora/20/html/Installation_Guide/Create_Btrfs-x86.html

Seems to have gone succesfully. My 1.9TB /home volume which is 277GB used took about an hour to convert.

I only converted /dev/mapper/fedora_localhost-root and /dev/mapper/fedora_localhost-home  As per instructions on the 1st blog post listed above.

I used the Fedora-Live-Desktop-x86_64-20-1.iso and burn't it to a DVD using Brasero to boot and run the btrfs-convert process.

On first login the Dropbox client prompted me to rerun setup, which I did accepting the defaults and now it appears to be re-syncing. I'm fairly sure it's not redownloading but just checksumming what was already there.

Being a newb on btrfs I found this useful https://btrfs.wiki.kernel.org/index.php/UseCases