Since I made the move from Raid6 to Greyhole I decided to get involved in the project's development. Up until this point it's all been developed through the tireless efforts of one man, Guillaume Boudreau. I already made a commit which made it into the latest release of the project, 0.9.0, which allows you to find orphaned files on storage volumes (the main benefit being you can have prepopulated volumes you add to the pool without the need to have bulk quantities of files make the long journey from remote share, to landing zone, and finally to one or more storage volumes).
Next up, now that I know my way around the system quite a bit better, I did a bit of an overhaul to the fsck framework of Greyhole. It now supports being passed storage volume paths as well as share paths. So you can pinpoint target exactly what you want to fsck. This is all part of Issue 50 on the google code page. I hope to keep cranking out improvements to the project, it's the first time I've officially committed code!