the only thing holding it back from wide spread adoption I think is the fsck
That's a very big "only" IMO. I'm not about to install a file system that doesn't have a reliable recovery utility. It's a shame that politics has prevented ZFS from being widely used in Linux; it offers everything that btrfs does, and more. And it is now a very stable and reliable fs.
This sort of thing is why I prefer FreeBSD to Linux.