Aside from the "needs many gigs of RAM, even without deduplication turned on" angle, the lack of ECC memory would prevent me from using ZFS on raspi.

Sooner or later you will trash your data unless you're using ECC memory (which the Raspberry Pi RAM chips are not): http://louwrentius.com/please-use-zfs-with-ecc-memory.html

For the record, I also think it's cool to get this compiled and running on RasPi; just wanted to add the ECC info for anyone now thinking of doing something with this in production :-D.