I use the macbook pro 14 and this rucksack is ideal. I don't want something that is a tight fit because I carry other things in the bag, such as a couple of files, maybe a magazine and a bunch of cables and usb accessories. Basically my rucksack is my mobile office!
I think you could probably get a MBP16 the bag just fine but the optional velcro strap helps secure my 14 inch MBP. To be honest I don't use it because it is secure enough for me.
But anyway a few features to highlight are: (1) the padding on the outside of the bag on your shoulder blades which increases the walking comfort (2) the laptop slot padding which is not too much but just enough without bulking it out. (3) optional velcro strap to hold laptop in place (4) lots of compartments and pockets to keep things separate and organised (5) strong zips with decent handles on them - I don't know if it's just me but zips on other bags are always the first to break (6) 2x side bottle pockets with clip (7) the padded but robust carrying handle, I like the way it keeps it's shape and doesn't dig into your hand (8) the hanging hook for the gym locker (9) the security pocket in the rear which is ideal for securing my wallet when tube commuting.
I don't think these features are highlighted in the product so I hope this helps someone thinking about this rucksack.