Heya! So, it's hard to know precisely re: 1.0, but I'm anticipating approximately towards the end of the year. Federation is the big thing we're still waiting on until we consider ourselves 1.0-worthy. Probably we could have tagged ourselves 1.0 a while ago and considered federation 2.0, but federation is at the root of a lot of our goals, so...
Anyway, once all our summer projects wrap up, I think we'll have reached 1.0-worthiness, however there's a lot of code being developed right now, and I can't promise how long it'll take for it to hit the "quality approval for merge" state.
We've had theming for a while, since 0.3.1! http://mediagoblin.org/news/mediagoblin-0.3.1-a-whole-new-lo...
Read the documentation for details on that, but you can already enable a light "airy" theme if you prefer.
PS: If you're a python developer and interested in federation, you may be interested in checking out our super-awesome-contributor Jessica Tallon's "PyPump" library, which integrates with the Pump API: https://github.com/xray7224/PyPump
I know she wants more users and feedback! Pump API integration is on the way, but in the meanwhile, there's a project that's already using it if you want to try out the API: http://pump.io/
Thanks for the excellent questions! Hope that rambly response was helpful :)