Google Drive just got an activity stream that details everything you and the people you're working with have been doing with your documents and spreadsheets.
The google drive desktop client is buggy. It seems to like to "disconnect" on me randomly, and sometimes things just don't sync for hours at a time. I wish they would work on that a little bit before adding new features. Dropbox has always been rock solid and as a result I ditched GDrive and bought more dropbox space.