Just another quick heads-up; Woot is at it again with a good deal on outdoorsy gear from Maxpedition. Right now they're selling some Gearslinger packs at pretty good prices. The have the Sitka for $59.95, the Monsoon for $69.99 and the Kodiak for $79.99!
I have a Kodiak that I've had for many years and iirc it was around $140 when I bought mine. The construction is fantastic and mine still looks basically new. It's main use was as a book bag & laptop case when I was in college but it's had some dirt time as well. The knock I will give it is that the Kodiak is really too big to be a sling bag (ie with just one strap)- if you loaded it up fully it was uncomfortable to carry around. I may try a Sitka though at this price!
No affiliation, just a Woot junkie and Maxpedition fan.