ZFSonLinux has finally added a repository for Wheezy, so when OMV comes out on Debian 7 it will be dead-easy to install without even having to compile:
http://zfsonlinux.org/debian.html
Package is called debian-zfs.
Hopefully this will help get zfs included in OMV on Wheezy.
ZFS pools don't auto-mount under Debian like they should; you have to run /etc/init.d/zfs-mount, but it works fine after that.
-Wes