Earlier in the mailing lists we were discussing GUIs for O3X, and I could imagine three separate programs that could be useful. Or not?
1: Installer.
Already done, and works well.
2: Control Panel / System Preferences
O3X could probably do with having one of these, for system wide things. I could imagine at least having version display (kext too), arc.max setting, autoimport toggle, and various ZED tweaks.
3: Actual ZFS GUI
Referring more specifically to the usage of ZFS. List drives, create pool, status, add/replace vdevs and that sort of thing. I personally dislike writing software for just one OS, and here there is scope to write something that would work for everyone. There also exists some implementations already (zfs.guru at least, but 'php'). This is a larger/separate project for sure, but still interesting to think about.