Update: About ZFS in Squeeze (2)
The bad news is that you won’t be able to use ZFS as your root filesystem in Debian Squeeze with the official installer. The blocker is missing support in GNU Parted. Unfortunately the patch I sent in August wasn’t integrated in time for the freeze (and still isn’t, but there’s no hurry now, it’ll hopefully be there for Wheezy).
The good news is that all fixes required for the installed system (including ZFS userland utilities and GRUB) made it and are already in Squeeze. As a result, the unofficial installer I built in September will (unless something weird happens) continue to work during Squeeze life cycle. Note that although the installer itself is modified, it installs a pristine Debian GNU/kFreeBSD system from official packages.
Hope this is helpful to you if you plan on deploying ZFS in your organization and the other approaches don’t fit well enough with your needs.