I'm an addictive bag buyer. This is my favorite, and my preferred size:
http://duluthpack.com/school-campus/backpacks-bags/messenger-shoulder-bags/field-satchel.html
What I like about this one is that it has lots of pockets and dividers--film, hoods, etc, all separate. A big divider down the middle to keep some things from smashing together. It's not a camera bag, and in general I don't like bags with assigned places for things. I rely on individual containers for lenses--sock tops with one end sewed shut, or heavy-duty freezer zip bags, and throw it all in together, along with, often, a book and my lunch, so regular divided bags don't suit me well.
I don't usually carry a lot of stuff--at
most two bodies and four lenses, and more often one body and two or three lenses, so space isn't a problem. If I have a lot, I bring two bags to distribute the weight.
When I was a news photographer, cameras and lenses went on one side, and flash equipment on the other, and I didn't have to carry the flash gear all the time, anyway--it often stayed in the car.