It's in. This is one of the big features for 8.1. I'm not sure of any project where I can use it right now myself, but it has been asked for a lot, so I'm sure it will be popular. I'll just have to figure out something to do with it myself.
Looks like we might have a different default database for tools to connect to in 8.1, to get around the "connected to template1, can't create a new database" problems that happen in previous versions.
On top of that, a generic database for tools like pgAdmin to store their config in - wether included by default in an installation or just an agreed-upon shared database name and structure that tools will autocreate.