Migrating ext3 to ext4 on an encrypted root disk (ubuntu 9.04)

Ext4 is supposed to be much faster than ext3. Anything that makes development of EJBCA a bit quicker is interesting, so I just had to migrate to ext4 now that Ubuntu 9.04 is out.
The usual ext3 to ext4 migration guides are for normal unencrypted disk. Since my laptop has full disk enryption a few addition steps are needed.
Also the guides mention that you have to do 'grub-install' after migration. I did not have to do that.
Either it is because:
- I only migrated / and not /boot
- The standard upgrade to Ubuntu 9.04 already installed a new grub for me.

Anyhow, here are the steps hwo to migrate an encrypted root disk from ext3 to ext4.

Shut down computer properly, don't hibernate.
Boot from Ubuntu 9.04 cd and use it as a live cd (no changes to computer).
Open a terminal and become root.
#sudo su -

Set up crypto add encrypted disk to lvm
#cryptsetup luksOpen /dev/sda1 root
#lvm vgchange -a y

Mount root disk and just check that it's the correct disk before migrating
#mkdir /mnt/root
#mount /dev/tlap/root /mnt/root

Unmount and do the migration to ext4 (as described in the ext4 wiki and numerous other sites)
#umount /mnt/root/
#tune2fs -O extents,uninit_bg,dir_index /dev/tlap/root
#e2fsck -pfD /dev/tlap/root

Mount new ext4 disk and change fstab to ext4
#mount /dev/tlap/root /mnt/root
#cd /mnt/root/etc/
#vi fstab

Change ext3 to ext4 for you / disk (/dev/sda1 for me).
# /dev/mapper/tlap-root
UUID=ca86bf3d-40fb-4b4d-89c6-15ce94674fa0 / ext4 relatime,errors=remount-ro 0 1

Save, unmount /mnt/root and reboot.
After reboot check /etc/fstab and 'mount' and you will see that it's ext4 now.

tomas@tlap:~/tmp$ mount
/dev/mapper/tlap-root on / type ext4 (rw,relatime,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
...

Update:
I migrated my rather slowish home computer (AMD 4200+, 4GB, WD Raptor) running 'ant clean; ant' both before and after migration. The conclusion is that it takes 1 minute, give or take a few seconds, on both ext3 and ext4. Not huge leaps in speed there unfortunately.