Here is a list of changes in different AKU versions.
http://www.mobile-review.com/pda/art...m-aku-en.shtml
Most notably are faster boot time, they cut 15 seconds off of boot and faster screen switching, portrait to landscape.
One other advantage of AKU 2.2, you can remove the battery from the today screen and put the time/date in its place.
This link also has a review of AKU 3.0
-Paul