I'm seeing a lot of ads online for Corning Gorilla Glass. I just got an iPhone 4 last month, and immediately had a Zagg Invisible Shield applied to the front and back AND put on a bumper case. Is the Gorilla Glass sufficient on its own? I mean, is it as scratch resistant as the iPad? If so, I am thinking I might not need the Zagg. I've let my cat and dog play with my iPad, and there's not a scratch on it. And I've had it since April. I don't know...I really would like to just enjoy the glass if possible.