I should have noted that I did use it exclusively as a purse on a 4 day trip last week, and it worked out fine. I was able to carry the bare minimum that I would carry in a regular purse, though it was a tight fit. I also wouldn't recommend a regular wallet in there, for the same reason as the Mighty Bright. It can be done (at least with a non-checkbook size), but it bulges out and isn't easy to put into or out of the pocket.
I do think that short of serious overstuffing or a hard knock, the Oberon + the travel bag is about as much protection as you're going to get for the screen, especially if you leave the stiffener plastic in the front cover of the Oberon. The cover really helps to spread any mild impact across the entire front of the Kindle, which means most of it will impact the frame. Obviously nothing is going to survive a direct hit, so don't fall on it or accidentally smack into a wall with it.
Also, once your Oberon is in the main section, there is about an inch of space between the top of the Kindle & the zipper. IF you're careful, you can use that space as well. I've put my keys there previously, or the cable, folded to fit of course.