Great bag! I ordered one and was very impressed with the quality and ruggedness of it. Of course, my grandson confiscated it when his bookbag croaked and has given it a real workout. Looks like I'll be buying another one.
I've got as Maxpedition Falcon II that is a recent gift. It is OK. I've had a couple of Camelbaks and sold them. Alice pack? I like it for the motorcycle rack but not to carry.
My most used? Still an Arc'Teryx. I've got an Arro 22 that has been abused for almost ten years. Black, ay water resistant and you can be very mobile/active while wearing. Check out the Arro 22, Miura 20 & 30, and the Arrakis.
I was going to say an Alice pack but many peolpe here already beat me to it. In the service and they are as good as you're ever going to get and are a steal at twice the price. You mentioned a medium sized backpack, but I'd recommend buying the large and not filling it up as much.
I'd also recommend camelbak backpacks. I've still got the motherlode I took overseas and as much as I abused it, it's still in great shape. Currently I keep a camelbak BFM in the back of my vehicle holding my roadside emergency kit. I also use this backpack for hunting trips and I love the BFM. FYI the side pockets on the BFM hold five or six 30 round mags in each pouch. What's not to like about that?