You can set notifications to find out when your collaborators have modified your spreadsheets, and learn what sheets or cells they've modified. You can also choose how often you'd like to be notified.
TinEye is a great reverse image search online service, that can tell you where an image came from, find different sizes of the image and you can find out if someone is using your image without your permission.
If you are a Nokia N9 and its Meego OS fan then this should really be a big deal for you and all the people that are still open for alternatives and new players on the smartphone market.