I've gone from an iPad 2 wifi only model to an Air with cellular. I've not had a cellular model before so the plastic antenna cover on the back is new to me. Now, when I run my fingers along the back of the iPad it feels like there is a very small but definite ridge where the plastic of the antenna cover meets the metal of the rear casing. It's enough to stop a fingernail in its tracks. To be honest it feels very un-Apple and cheap. Is this normal, or do I perhaps have one that hasn't quite been assembled properly? I keep wanting to push the antenna cover in so it's smooth!