Its a little on the pricey side but it's of the highest quality and I dont mind paying a little more for something thats gonna last.
My partner and I both use a
Tumi backpack.
It fits comfortably: Canon 5D and Canon 50D with lenses attached (both
wrapped), 2 speedlites, 70-200 lens,
3 pocketwizards, snoot, cables, wire trigger, tripod connector, (16) AA batteries and 2 chargers, (3) canon batteries and charger,
business cards, pens, gels, and my laptop.
It also doesn't scream "I'm a camera bag! Come steal me!"
I have a black one which is cool, but my partner's is BRIGHT yellow which really stands out if someones running away with your bag in the airport, then you can yell "stop the guy with the yellow bag!" or "That's my yellow bag!"