I have just received my Backpack and the quality is really good my only quibble is that I would definitely have your retina macbook in a sleeve and then inside the backpack as there is little protection to the top of the rucksack. I removed some padding strips from an old laptop case and will fitted them at the top before I travel to Spain, just to ensure it does nt receive any knocks in flight. A Magazine in front would also help cushion.
The bottom seems fine and the back is super padded and very very comfortable to wear, I love the iPhone/ipod pouch and hidden compartment on the back which I will use for passports and other travel documents.
Very Smart looking backpack.