A huge fan of Tactical 5.11 Rush72 [1] here. My favorite features:
- large in volume (55L), yet I can board a plane with it
- side pockets can be easily opened even if the main compartment is fully packed
- easily accessible and large front admin panel
- waist straps can be folded and hidden inside the bag
- the zip around the main compartment goes around all three sides, which allows very easy access for packing, unpacking or activities like having a picnic
- space between admin panel and the main compartment allows for extra external storage. for example, today I was carrying a small carpet bought in IKEA in there.
- wide straps which feel comfortable also with heavier loads
- looks ok also in a city, especially darker versions
- plenty of internal pockets everywhere
- dedicated back pocket for a laptop.
The only downside is that I'm not sure if a 15" laptop would fit into the back pocket. I'm using a 13" laptop and it fits. However, the backpack is so feature-rich that it's ok for me to put the potential 15" laptop to the main compartment - there's a half-pocket that can be used for that purpose.
All in all, this is by far the best backpack I have ever used.
[1] https://www.511tactical.com/rush-72-backpack.html