I also travel a lot, and have spent a few thousand dollars over the years, looking for the perfect bag. My biggest recent problem with travel is that I go into a lot of smaller airports (Santa Fe, NM, for example) where the only flights are regional jets, those with two seats on one side and one on the other -- and you can't get even *small* hard carry-ons in the overhead. So, they make you check them at the gate. I tried lots of different bags and packs, and ultimately, decided I had to downsize the equipment -- for air travel, now, I shoot Panasonic m4/3. I can get three bodies and seven lenses in a briefcase-sized bag (Think Tank) that will go in the overhead of a regional jet, along with a separate briefcase that contains the laptop and other stuff. You do have to let go of the idea of ultimate image quality, but I've done that, and it's come as a great relief.
JC