Murray,
I use almost exclusively Think Tank bags and have used them in the last 24 months to go to Colombia, Hungary, London, Austria, France and within the US.
I have used the Airport security and have always gotten away with getting on. Air France gave me a bit of a problem last year, but once I opened it, asked for a manager and showed them what is inside they were totally cool. Be careful what you wish for though. This bag holds two H2's w/ digital backs, four H lenses, two Canon 1Ds Mark II's, three canon lenses (50, 85,& 24-70), six batteries for the PhaseOne, Six Batteries for the H Body, three Canon Batteries and all the chargers needed for all this. Plus, four pocket drives and the 17" in the stretch pocket outside. It WEIGHS a TON! But if you need to travel with all this gear on it will work. I have flown on large jets to local commuter puddle jumpers.
I got the Airport International about a year after heavy duty use of the security and it holds almost as much. Minus one body of each system, two H lenses, one Canon Lens, and one HD. But the rest of what I put up top fits in the International and I have never been questioned or stopped with this bag. Other than the usual x-ray scan check. Every time I go through it never fails that they do the bomb swab wand test.
The only other bag I liked out of the dozens of bags I have used are the Lowe Pro series. The funny thing is one of the Principles of ThinkTank came from LowePro. In my opinion they have come as close as you can to perfecting the camera bag. The only other is a Gura Gear but it won't hold a laptop and it has no wheels. A true backpack for trekkers. If you can stay on paved walkways then the no brainer is Think Tank.
best of luck.......