Wow, that's so weird. I used the bumper for months and the back is completely scratch-free. I haven't tried to deliberately scratch it, but it seems pretty scratch resistant.
Weirdly, though, I don't care about cosmetic scratching to anything but the display. That I want scratch free. The rest of it can scratch all it wants. I think old, scratched up devices look pretty good, actually.
I switched the Griffin Reveal mainly because the bumper case was not flimsy, but stiff, and pressing the power and volume buttons took more pressure than the bare phone does.
It's weird that our opinions of the bumper case are so divergent. When I discovered the bumper case I thought it was going to be like the ones Apple used to sell for the iPhone 4 and 4S, so maybe that's why I don't think it flimsy.