I have had the 15" rMBP and now have the 13" rMBP and both have been damaged/dented easily. I don't even remember damaging the 15", I just noticed it one day while using it. On the 13" I, accidentally, very lightly tapped a glass bottle on it and it dented. I have owned aluminium MacBook Airs and Pros in the past, and I have never damaged one of them in this way. None of them have been dented at all after a lot of daily use because I am careful with them. It seems strange that the new rMBPs are being so easily damaged, so I wonder if softer aluminium is used on these. Another point that I forgot to mention is that the aluminium on the rMBP feels smoother, whereas it feels more texturised on the Air. It is not a huge difference, but there does definitely seem to be a subtle difference. This also leads me to think that the material is different on these two machines. If I could I would go back to the Air, but I just can't get used to the lower resolution after using the Retina display for months.