I noticed a general update of the Google Reader UI this morning.
There's now a gray arrow button between your list of subscriptions and the reading panel, just like the one in Google Maps between your map and the search results. Just like in Maps, clicking it will hide your subscriptions list, replacing it with a 'My Subscriptions:' dropdown.
It's a nice UI tweak that gains me an extra 30% - 50% of horizontal reading space when I'm going through my feeds in the morning.
They've also updated the blue 'loading' dialog, replacing the blue beaker with a smaller orange loading message that sits at the top of the page.
I've seen this update come-and-go all morning, so it looks like they're in the process of testing / rolling it out.
Update (6 Sep 2007): They've also added search functionality! You can now search through any of your folders to find specific feed items. Neat.