We have recently prepared a KB article on the subject: How to use the new Allow/Deny permissions policy in the existing project and hope to hear your feedback on it and this new Allow/Deny security feature in particular. If you have not yet heard about it and its possible benefits for your project, I recommend you review the Concepts > Security System > New Security System > Permission Policies documentation along with a short overview video on our YouTube channel.
As a side note, a quite popular How to hide individual navigation items and groups for certain users example was updated to use the new PermissionPolicyRole class.
As always, our team is more than happy to learn more on how our security module can help your business better or assist in case of any difficulties. Feel free to contact us via the Support Center: https://www.devexpress.com/Support/Center/Question/Create or in comments here.
See also this post from our old customer http://www.codeproject.com/Articles/1153095/How-to-migrate-DevExpress-XAF-SecuritySystemUser-t for an alternative migration procedure.