Oh yeah. ZFS is mature on a whole different level than BCacheFS, too. As a bystander and potential user, if I have a hope for BCacheFS it's once it makes it into the mainline kernel, it attracts more developers and grows into a community project with versioned releases and all that. I imagine that its author hopes the same.
(Obviously I'm not comparing anything to Bepsilon - they are irrelevant until implemented as an actual linux filesystem)