Couple thoughts... Square cases almost invariable hold less well in the hand than one where at least the outside edges (back of the phone) are curved. Even a slight bit of a curve goes a long way toward making the phone palm easier, more comfortable to hold, and feel smaller. For instance I have a Dilex and a Neo for the N5 and the Dilex feels smaller in hand than the Neo even though it measures out slightly larger. Also while Aluminum may at first seem like it would offer good protection a phone is saved in a drop from two things, cushioning to help absorb (some) energy before it is transferred to the phone and then also transferring that energy that does reach the phone to a wider area so total energy transferred at any one point is lower. There is a reason why most case makers use a similar formula with a hard but not completely stiff outer shell combined with a rubber/neoprene/silicon inner shell on cases that are designed for protection.
Course if you are after looks and this is working for you then its a win but if you want protection you might want to do some more research.