On the other hand, I think that file systems are closer to the heart of a database company than quite a lot of other Sun technologies (e.g. JavaFX). Oracle does sponsor btrfs – which is even more in its infancy.
Also, Jeff leaving doesn't necessarily mean that ZFS is dead to Oracle. Maybe he left because they decided to focus more on btrfs, maybe it's just a personal issue.
Indeed, 20 years at one company is a long time, plus his personal financial upside became strictly capped to salary once Sun was assimilated by Oracle. There's all sorts of reasons he might jump at a new opportunity, many of which don't mean the end of ZFS.
You should try putting it through its paces before coming to that conclusion; I've heard different things from other people, and I currently use it for my media storage.
The problem is that for this type of thing credible reports of failure carry more weight than reports of success. If you're making a big bet on the reliability of file system you want to mitigate risk, and for all I know either you haven't tickled a bug I would or you've just been lucky so far.
When I looked hard at this 2-3 years ago, it was clear to me that without a tape backup system I couldn't justify purchasing, ZFS just wasn't there yet. I've heard nothing since them to convince me it has been sufficiently polished to get over my threshold or required reliability.
ADDED: I don't think it can be said that ZFS is established to the same degree that the parent's examples are (Java, BEA and Oracle's DB).
Also, Jeff leaving doesn't necessarily mean that ZFS is dead to Oracle. Maybe he left because they decided to focus more on btrfs, maybe it's just a personal issue.