One of the gems that i came home to was the release of Google Reader's search feature which many of us had been begging for. The ability to search through all your feeds (from the moment you subscribed to them) is awesome and much needed- i am always looking for that blog post "i read the other day". Another good use that i have already put into practice (principally because i have thousands of unread feeds at this point) is to do quick searches to see who is writing about topics that i might be interested in currently.
I would like to see other features beyond more advance search features, like the ability to save and share searches and APML support.
Steve Rubel posted an interesting post on How to Data Mine Google Reader Feeds for Trends, which is yet another way that these new features can be used.
Rubel via Jeremiah's Twit on Rubel's post.