I've handled the Streetwalker in a shop, but I've never seen the Crumpler bag. Looking at the two online, the Streetwalker appears to hold far more gear, so some of this may depend on what you need to carry. The Crumpler doesn't look like a camera bag, which in my mind is a nice feature.
Comments on the ThinkTank bag: it has some of that bulky "photo backpack" look and feel. It is extremely well made -- all my ThinkTank gear is bomber and well designed to boot.
I'm 6'2" with a long torso, and none of the carry-on size photo backpacks fit well. Since they max out at 22-inches tall, they simply aren't tall enough to use the hip belt in the right place.
The only time I use a backpack is when I have to travel for an assignment, and I can get away with the minimum amount of gear. Then I take my favorite pack, the LowePro Stealth AW, the original model with the neoprene pouches for gear. It will hold two bodies and three pro zoom lenses with hoods, a 15 inch computer, all the accessories, and a day or two of clothing. The Stealth looks nothing like a photo backpack. There is a current ThinkTank model, the ShapeShifter, that is very similar (and I think was designed by the same person who made the Stealth.) Holds a 17-inch Macbook Pro, 2 bodies, 3 lenses, accessories, etc., in a kit that doesn't look like it's full of photo gear. The downside to either of these packs is that you can't work out of them, they are just for carrying gear -- but that's true of most backpacks.