If you’ve implemented the Shared Users Table trick you know that there is a side effect: Users on one blog are not immediately given privileges on the others. To resolve this I wrote a little plugin, WP-Orphanage, that will promote these ‘orphan’users to a role of your choosing.
WP-Orphanage v1.2 has been released. It addresses a nasty bug where only the first 50 users were promoted. I have refactored the code to iterate over the full list of users. This action only takes place when an Admin visits the User page. Users that login to a blog where they have no privileges will continue to be given a role “just-in-time”, when they login, but if you’re looking to upgrade all your users in one go, the plugin will now oblige. This is a recommended upgrade for all users. Thanks to everyone who reported this issue!