Knowing Btrfs is still not default file system in any mainstream distros, I have 2 machines using it. I just love the features of subvolume, snapshot and COW (copy-on-write).
I'm not talking about everyday operations here, which (except system boot though) are hard to tell the difference between Btrfs and Ext4. When you do a major update or distribution upgrade, be aware that it may take much longer time than you expect.
I'm doing the upgrade from Ubuntu 12.04 Precise Pangolin to 12.10 Quantal Quetzal Beta 2. It took about half an hour to download new packages, which totally depends on your network bandwidth. But it's been 5 hours and the progress bar is just over half in installing the upgrades step.
I can expect the upgrade to finish within another few hours, which is not as bad as another user's experience. I don't think this issue will get addressed before Btrfs becomes default in Fedora or something, but it definitely should be solved before it becomes default. The question is, chicken or egg?