Okay folks, as of a couple hours ago unified login is available opt-in for all Wikimedia accounts!
In addition, we’ve enabled the site-wide global session cookies (which have been in testing for the SSL interface on secure.wikimedia.org for a few weeks). Some people may not be able to successfully get that working across domains (we’ve got reports of Norton blocking the login-cookie-fetching images), but it seems to be working for most people so far. :)
This means that not only will your global, unified account have the same password on say English Wikipedia and Commons, but once you’ve logged in on one you’ll be logged in on the other, without having to log in a second time. Handy!
Note that to do this fully automatically, when you visit a new wiki for the first time it will autocreate a local account for you, linked to your global account. Initially this was spamming the Recent Changes lists with account creation logs, but I’ve now pulled that (they’re still logged in Special:Log, however). (This has been disabled for now, as it’s spamming logs and user lists faster than expected, even through “invisible” links like shared JS and CSS. You’ll still get your shiny local accounts by going through the regular login form, and once you’ve done it once your sessions remain shared.)
Big thanks to Tim Starling who’s done a huge amount of work on CentralAuth in the last couple months, as well as Andrew Garrett who’s helped a lot with the cross-domain cookie logins and global Steward group management.
Way to go Brion!
This is the most important single improvement ever to making the Wikimedia projects easier and better to use.
Way to go!