On the search side, the split isn’t as high. If you use AdSense for Search, you only get 51% of the ad revenue. Google attributes this difference to the higher costs involved in hosting search results on sites other than their own plus all the added stuff you can do with AdSense for Search, such as restricting searches to a specific set of sites, etc.
Revenues for the other AdSense variants have not been disclosed and are apparently subject to change and experimentation as they develop.
Of course, big AdSense publishers have always been able to negotiate revenue share and get access to custom ad formats and other features, and that information is still confidential.
This news definitely interested a lot of publishers. Note, however, that Google doesn’t really mention they’re not doing this out of the goodness of their heart — Italian courts were going to force the issue in Italy, so I guess they figured it was just as well to come out clean across the board.
I will let you decide if the 68% and 51% shares are high enough or not.