Sometimes it’s nice being wrong. Contrary to what I predicted, ZFS will be supported in Debian Squeeze using the official installer.
This means that Debian Squeeze will be one of the first GNU distributions to support ZFS.
In fact, even though ZFS support didn’t make it to Debian-Installer beta1 by the time it was released, it is now available in the netboot images (this happens because netboot images fetch newer installer components from the internet).
As a consequence of this my unofficial installer can now be considered obsolete.
So why did I say something that turned out to be grossly inaccurate? It’s not due to anyone’s fault really. At that time, the version of Parted that included ZFS detection hadn’t migrated to Squeeze. The unblock policy didn’t appear to allow this migration. However, the Release Team kindly decided to make an exception that allowed this, and after Parted had migrated the changes in Debian-Installer itself went in quite smoothly.