We've had a very positive experience with btrfs, using it on a redundant system for a few years. It's a lot more flexible than zfs in some respects. For instance, all the snapshots are modifiable and can themselves be modified. You can build up a graph of snapshots, which is not possible in zfs which enforces a strict hierarchy. We ran btrfs on top of mdadm, to get raid and integrity checking.

btrfs can do things like copy particular files using copy on write, which is really cool. btrfs also supports offline deduplication, which isn't supported in zfs. This is very useful if you want to do the deduplication when the system is not otherwise being used and avoids the overheads of keeping hashes in memory all the time.

I think that 10 years behind is exaggerating where it is at. For instance, people using zfs on linux often have problems with running out of memory and so on, even on systems with very large memory.