I've had mine about 3 days now. I'm easily getting the advertised 7 or more. Brightness around 70%, a few Safari windows opened, even copying some files back and forth across the network doesn't seem to be hurting anything. As I type, I have 78% remaining after about 100 minutes of working on an essay in GoogleDocs and browsing around for research info at the same time (plus getting distracted at MacRumors).
All that being said, my projected time does tank as soon as I start watching videos on Youtube...