I agree, the frontpage of mediagoblin.org can use some improvement. We're working on that. If you want a fast summary of things, you can still watch the video from the crowdfunding campaign we ran last year with the FSF (hell, you can still donate too!). http://mediagoblin.org/pages/campaign.html
We also have an intern helping us clean up the homepage. Things should be getting clearer soon, I think. I agree that http://mediagoblin.org/ could use some improvement.
In the meanwhile, if you're wondering what it offers, right now it already supports nice photo, video, audio, document (pdf.js!), and even 3d model support. It's written in Python, so it's easy to get hacking on. We have a lot more exciting things on the way too, most noticably federation; we currently have someone working full time on adding federation via the Pump API: https://github.com/e14n/pump.io/blob/master/API.md
This will make it so that even though there's a bunch of separate MediaGoblin instances out there that you should be able to have a lot more of the same social features of other media hosting sites as if they're in the same place.
I'm happy to answer questions if anyone has any!
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 :)
Will it support easy mirroring of media? Will the site be also metaservers (servers that provide the addresses of other servers), or proxy servers (they serve the content of other servers they know of)? What about the bandwidth issues (often bandwidth is asymmetric between upstream/downstream)? Maybe some form of load balancing by redirection to another server. But one would need URI scheme across all the sites... Oh my.
Also: one-click-install for Windows/Mac when?
Re: mirroring, I replied to that a bit here: https://news.ycombinator.com/item?id=6180159
Additionally, you can already host media files with an OpenStack Swift cloud files provider like Rackspace Cloud if you prefer.
I don't know anything about windows or macs personally, though people have gotten mediagoblin working just fine on macs... windows is harder. :) I don't have any clue when that packaging might happen though... if it happens, it'll be by someone else I guess; I just don't know anything about it.
And in any case, it's not just a "oh, we tossed an intern at this"; in this case, the person who's working on this is a community member and intern, and is doing work based on a detailed analysis based on another community member's work overviewing all our current messaging: http://lists.mediagoblin.org/pipermail/devel/2013-July/00061...
So it's not just a matter of, "oh get an intern and toss them at it"!
But hey, if you're bothered by the fact that we're a community project with not a lot of full time resources, you can donate and help us pay for more people to come on as dedicated resources! The crowdfunding campaign we ran through the FSF last year is over, but the donation link still works: http://mediagoblin.org/pages/campaign.html
Or, feel free to help us out yourself! http://mediagoblin.org/pages/join.html