I think that it is a little odd that after clicking "OK" on a "You Shall Not Pass" dialog, I am redirected back to the home page. I think it makes more sense to be redirected to the previous page that was being viewed.
For example, if I go to https://secure.phabricator.com/diffusion/ and click on "New Repository", I end up on https://secure.phabricator.com/diffusion/new/ with a "You Shall Not Pass" dialog. I click "OK" and am taken back to https://secure.phabricator.com/, whereas I would expect to be taken back to https://secure.phabricator.com/diffusion/.