I used a Speck see through hard case on my 2011 ultimate air and it was decent in the fact that it protected it. Now I use a case crown. I for one cant fathom how people spend thousands on this beauty and dont protect it. With this case or any case the big advantage is that you can place it where ever you want without the fear of aluminum scratching. Aluminum contrary to fanboy belief, does scratch very easily and it would be sad if mine did.
Just go look at the new chargers at the Apple Store and how bruised up they look!