You can't export the content of the feeds (EDIT: using Google Takeout, that is.) Oftentimes, GR is the only one that still has a copy of an older article. What use is it to know I've starred an article if I can't read it anymore?
(To remedy this, I've been using Reeder to export all my starred items to both Instapaper and Evernote. But no thanks to Google.)
I'm a day or two away from "finishing" a script that will allow you to do that (well, at least as far as Google will let me) and pushing it to Github. I'm likely not the only person working on this so I expect we'll be able to save most of our data.
My first resort when someone deletes their blog or whatever thing that was meaningful to me that I foolishly failed to mirror, is to go to archive.org and see if they have a good mirror. If they don't but they do have enough that you can find out the RSS URL, you can get google reader's archive of the feed like so: http://webapps.stackexchange.com/questions/17484/archive-exp...
Closest thing you can do is grab the JSON of the data as the browser downloads it. The cached content that shows up on a feed's pane is transferred in bulk via JSON, so it should make a decent archive.
(To remedy this, I've been using Reeder to export all my starred items to both Instapaper and Evernote. But no thanks to Google.)