I’m really growing to love Google Reader!
The interface is fantastic. The keyboard shortcuts make using it a joy (not to mention, really fast).
Normally one of the main drawbacks of an online RSS Reader is that you can’t use it when you are offline (on a train, plane, whatever), however Google Reader overcame this shortcoming by launching Offline functionality in Google Reader. You can now read the last 2,000 posts while not connected, if you need to!
What other features of Google Reader are there which I neglected to mention?