I have the Photo Trekker AW and it is huge. You might want to take a look at that bag as well.
How far are you guys hiking with your whole kit? I take what I think I'll need, and leave the rest in the trunk of the car. Basically ends up being the camera on the tripod over my shoulder with my dark cloth folded up to make a nice pad. Small backpack with my meter, a few film holders, filters, and notebook. I can't see hiking any distance with my whole kit on my back.
I always plan my trips to involve a mximum hike of about 5km with my gear (8x10, 6 holders, 2 lenses, accessories, and tripod), stopping now and then to rest or to just take in the surroundings. Most of the places I visit do not allow cars to come anywhere near them.
Sean, have you weighed yours with your gear in it yet? I tried out a Kelty 2650 at the sporting goods store tonight. We weighed it with my dorff 8x10, 4 holders, 2 lenses, meter and loupe and it was about 24lbs. Add 7.5 for the tripod, and I am over 31lbs :O I didnt like the way it fit my body, and am going to wait and see what their next shipment looks like (different bags). The kelty is a weekend hiking internal frame pack, and costs between $75 and $100 depending on where you get it,
I looked at the Lowepro bags mentioned here and spoke with an owner who found it a bit heavy. So I opted for a Kinesis Journeyman. It holds my Arca-Swiss F-line, 5 lenses, filters, film, cloth, extra bellows, etc, and weighs 25 llbs. The harness is IMHO much more comfortable than the Lowe Pro.