I tried btrfs on three different occasions. Three times it managed to corrupt itself. I'll admit I was too enthousiastic the first time, trying it less than a year after it appeared in major distros. But the latter two are unforgiveable (I had to reinstall my mom's laptop).

I've been using ZFS for my NAS-like thing since then. It's been rock solid ().

(): I know about the block cloning bug, and the encryption bug. Luckily I avoided those (I don't tend to enable new features like block cloning, and I didn't have an encrypted dataset at the time). Still, all in all it's been really good in comparison to btrfs.