I would assume that there would not be much if you dropped it on its back with the aluminum. However, it does have a much larger sheet of glass on the front. I would just suggest being careful with it like you would your laptop. I don't even like dropping my iPhone.
So obviously I'll have to treat it like my 17" MBP, rather than my iPhone. I've dropped my iPhone at least a dozen times, sometimes on VERY hard surfaces (NYC subway platforms), with never any problem. But I've never dropped my MBP; so that's the strategy I'll take with the iPad.
I wonder if Speck will put out a product for the back.