I have this backpack too. I like it. I'm with onelogue, it isn't a perfect backpack and some things I wish were a little different but it does everything I need it to do and the pros definitely outweigh the cons. Especially if you need to ride on base.
I can carry a set of gym clothes (shoes, socks, shirt, boxer briefs, small towel) and my food for the day in the main pouch. Check books, camera, gum and some other odds n ends in the upper outside pouch with room to spare. Earphones in a little pouch on the side. Lock for my locker on the other little pouch on the other side. Wrist wraps in on of the little mesh pouches that is on both of the side pouches that buckle in the back.
I wish it could hold little more. I would like to put an extra change of clothes to ride home in after the gym so I can shower there and not get my helmet/jacket all sweaty. I will probably get a tail bag sometime to help with this though.
I got the bag for $93 brand new. I'm happy with it. The rent-a-cops going on base were starting to not let me on without something bright colored/reflective so it was the first one that I saw that was almost all brightly colored so I ordered it.
Hope this helped and good luck finding one for a better price.
*Edit - and it has an extra shield pouch in the main cargo area.