When traveling all my camera gear goes in a Lowepro DryZone 200
backpack. (Tripod carried separately)
It’s a great bag. I usually have the Pentax 67II body with a lens attached plus two to four extra lenses, a Lee filter set, film, lens hoods, sunglasses and torch in the main compartment. In the outer compartment I have cleaning tissues, digital camera, audio recorder, batteries, business cards, tickets, AC cable for Ipod and sometimes a reflector.
The big advantage of the DryZone bags is that they have an extra zippered waterproof layer protecting the inner compartment. In theory you could drop your bag in a river and (as long as it’s zipped up) the inner compartment will remain dry (the outer compartment will be flooded). For me it’s more about heavy rain. If you are outdoors away from shelter and it starts to rain really hard that added protection against the elements is extremely useful.

Lowepro DryZone 200 (image from Lowepro.com)
My bag served me well for 7 years, but on the last trip the glue holding the zipper to the waterproof outer shell degraded and came apart, so that the bag could no longer be made waterproof.
I contacted Lowepro and explained the problem asking if it could be repaired. After a few emails assessing the problem they asked that I send the bag to the distributors in Japan. I was contacted a few days later saying that the zipper could not be repaired without compromising waterproofness and so they sent me a brand new bag free of charge.
In conclusion we have a company that actually lives up to the blurb on their website. Lowepro: great products and great customer service.