Hi Fred,
Yes, I often use my small Timbuk2 bag to carry my camera gear. I can carry my Bessa R (or small SLR) plus an extra lens, a compact digital camera, a small tripod, my iPod, a jacket, snacks, film, extra batteries for the digital and a paperback book.
The bag has no inserts of any kind but I have used the small interior pockets to carry my extra lenses. When I pack the bag I try to use my jacket or a hat to keep the cameras from bumping together. If you were creative you could make inserts on your own. The Timbuk2 bags don't have any "shape" -- they tend to conform to whatever you're carrying in them. This might make the application of inserts rather tricky, but I'm sure it can be done.
I like the Timbuk2 bag because it's simple and durable with the advantage that it doesn't look like a camera bag. I always wear mine "messenger style", slung across my chest and kept close to my body. This helps keeps the contents secure when I'm in a crowd or when I'm riding my bike. I can keep both arms free and I don't have to worry about the bag slipping off my shoulder. It's a great bag to use for walking or tourist-type photography.
There are only two things I don't like about the bag. One, small items like film cassettes have a tendency to find their way into the folds at the corners of the bag and can be hard to reach. Two, the bag is so well waterproofed that it will hold water inside like a pail. Be mindful of this if you carry a water bottle or other liquids inside the bag with your cameras!
Timbuk2 bags are expensive (even on the big auction site) but in my opinion are worth every penny. I've carried mine on several multi-day trips and I have had no problems. Highly recommended.