Effective today, I will be disabling the Node Access module, as well as the User Relationships Node Access hook. I don't see that anyone actually uses this access control stuff, and it should speed up the site to have it turned off.
Two kinds of access control will remain: Taxonomy Access Lite (used by the forums) and the Personal Book module. Only the former actually produces a performance hit, and it is rather small.
If anyone really can't live without the access control features (the "Grant" tab on your nodes), let me know and I will enable them again.
