I'm real happy w/ the AA backpack, so far. I haven't had to tote it anywhere, yet (having just gotten it in), but it seems to be built solid, and it'll hold a bunch of stuff. Its essentially the Airport International w/o the "rolling case" stuff (wheels, handle, security cable) - and hence is something like 4 pounds lighter.
I'd outgrown the Lowepro Mini Trekker I had (which was packed to the gills). I've been working out a packing arrangement for an upcoming trip to Yellowstone, and I added another lens, a small video camera, a Kodak Stereo Realist camera w/ film, a Sekonic light meter, and some RRS pano gear, and I've still got room for the 15mm fish, 1DMkIII (if I get it in time) + charger and extra batteries, and then maybe even a little more.... The only question will be if I can actually carry that much weight...
I have a Speed Racer belt pack, as well, that will serve as my main hiking bag, so I won't be carrying all of that around all the time, of course...