I might take a 7" tablet to do the following:
-Use as a Navigation System/Stereo in my car (Mount needed)
-Operate my Garage
-Manage my household, the lights, electricity, etc.
-Interact with my DVR at home
-Skype
-As another commenter said, sit in a bar/coffee shop and browse the web, check E-mails
-Mount to my PC or a projection system to I can use it to play games (but I guess they can't run Crysis yet, can they?). Built-in Kinect would be nice.
-Note taking (having a stylus for this would be nice) and using MS Office
-A built-in personal assistant (like Siri) would also be a necessity.