No idea about data2ext, never used it.
When I first installed IHO last Sep., I symlinked /data/app -> /sd-ext/app. And it's been that way ever since. No muss, no fuss, no maintenance, nothing. It works great for me but I wouldn't recommend it for everyone, because it ties your apps to your sdcard.
So here's what I plan to do... in alpha8, I plan to bind mount /sd-ext/app over /data/app just like alpha7 does with dalvik-cache. This should be zero maintenance and will eliminate the need for any of the *2sd hackery.
I can toss out a script to plate in /system/etc/init.d for testing if anyone wants to give it a shot.
Oh, and if you don't have an sd-ext partition, you really should. Especially when running ICS. Because that poor little internal MTD in the OV is just not made for holding everything that ICS needs. The ROM diet of deleting extra stuff doesn't help much in this regard because we're talking about the /data and /cache partitions, which aren't affected by the size of the ROM itself.