ZFS on 7.X CURRENT /usr refuses to remount after boot

ok, configs first
#cat /boot/loader.conf
acpi_ibm_load="YES"   # IBM z60m Laptop
if_iwi_load="YES"    # Intel wireless driver on IBM z60M
legal.intel_iwi.license_ack=1     # Intel binary agreement
snd_hda_load="YES"    # Intel High Definition Audio Driver
zfs_load="YES"  # load ZFS
vfs.zfs.zil_disable="1"  # x86 recommended config -
http://wiki.freebsd.org/ZFSTuningGuide
vfs.zfs.prefetch_disable="1"   # x86 recommended config -
http://wiki.freebsd.org/ZFSTuningGuide
vfs.zfs.arc_max="83886080"    # x86 recommended config -
http://wiki.freebsd.org/ZFSTuningGuide
vm.kmem_size_max="268435456"  # x86 recommended config -
http://wiki.freebsd.org/ZFSTuningGuide

cat /etc/sysctl.conf
# $FreeBSD: src/etc/sysctl.conf,v 1.8 2003/03/13 18:43:50 mux Exp $
#
#  This file is read when going to multi-user and its contents piped thru
#  ``sysctl'' to adjust kernel values.  ``man 5 sysctl.conf'' for details.
#
kern.maxvnodes=50000

cat /etc/rc.conf
# -- sysinstall generated deltas -- # Sat Jun  9 00:06:41 2007
# Created: Sat Jun  9 00:06:41 2007
# Enable network daemons for user convenience.
hostname="z60m.somedomain.com"
ifconfig_iwi0="DHCP"
moused_enable="YES"
moused_port="/dev/psm0"
moused_type="auto"
ntpdate_enable="YES"
ntpdate_flags="europe.pool.ntp.org"
sshd_enable="YES"
zfs_enable="YES"

cat /etc/rc.d/zfs
#!/bin/sh
#
# $FreeBSD: src/etc/rc.d/zfs,v 1.5 2007/04/22 20:55:08 pjd Exp $

now... as seen straight from the docs at
http://wiki.freebsd.org/ZFSQuickStartGuide

# echo 'zfs_enable="YES"' >> /etc/rc.conf

# zpool create tank raidz da0 da1 da2

# zfs create tank/usr
# zfs create tank/usr/home
# zfs create tank/usr/home/user
# zfs create tank/usr/lib
# zfs create tank/usr/libexec
# zfs create tank/usr/libdata
# zfs create tank/usr/bin
# zfs create tank/usr/sbin
# zfs create tank/usr/local
etc etc etc

# cd /usr
# tar zcvpf /tank/usr/usr-fs.tgz *
# cd /tank/usr
# tar zxvpf usr-fs.tgz


cat /etc/fstab

# Device                Mountpoint      FStype  Options         Dump    Pass#
/dev/ad0s3b             none            swap    sw              0       0
/dev/ad0s3a             /               ufs     rw              1       1
# comment out old
#/dev/ad0s3d            /usr            ufs     rw              2       2
tank                    /usr            zfs     rw              2       2
/dev/acd0               /cdrom          cd9660  ro,noauto       0       0

# echo 'daily_status_zfs_enable="YES"' >> /etc/periodic.conf
# zfs set mountpoint=/usr tank/usr


upon reboot, the system drops to single user with error message

cannot find fsck_zfs in /bin, /sbin


but from single user i can
zpool import -f tank
zfs mount -a
exit

and itll continue to multi-user mode

what did i miss ???