Just tested on CM7.0 data2sd from Blayo's ROM ...I can't run it! After data2ext --enable and reboot I get stuck on CyanogenMod logo... How did you do that ?
If you do it this way I cannot guarantee it will work, assume it won't. I will take no responsibility for anything that you do to your phone. If you copy and paste these commands without giving thought to what they do I will just laugh at you. I will laugh even more if it goes wrong. These steps are what I think I did, off the top of my head
Boot up CM
Connect to PC
Code:
adb shell
stop zygote
stop keystore
mkdir /mnt/asec/data
mount --move /data /mnt/asec/data
mount -t ext2 -o nosuid,nodev,noatime,nodiratime /dev/block/mmcblk0p2 /data
chown 1000.1000 /data
chmod 775 /data
cd /mnt/asec/data
cp -a app /data/
cp -a app-private /data/
cp -a backup /data/
cp -a dalvik-cache /data/
cp -a data /data/
cp -a dontpanic /data/
cp -a secure /data/
cp -a tombstones /data/
ln -s /mnt/asec/misc /data/misc
ln -s /mnt/asec/system /data/system
ln -s /mnt/asec/property /data/property
ln -s /mnt/asec/local /data/local
start keystore
start zygote
logcat
Then pray
This is basically what BlaY0's script does, I'm still working out a few kinks with the script for installing it. The logcat command is optional, but I like to know what's going on. With this it is all lost on reboot, but it should give you an idea of what CM is like with data2ext. Anyhoo, I've never scripted anything before, and some of these commands are meaningless to me, but I reckon I'll work it out.
TL;DNR:
With great friggin' difficulty. When I've worked it all out I'll post a version for CM

And like BlaY0 said, his script won't work on other ROMs
EDIT:
I have now made said zip. Try it at your own risk
http://forum.xda-developers.com/showthread.php?t=902395
/EDIT
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Check if there is a link /data/dalvik-cache pointing to somewhere else. If it is, remove it and reboot.
ls -l /data reveals no such links from dalvik-cache.