I'm the kind of photographer that likes bags. I have quite a few and I like the possibility to change bags for different types of shoots. Generally I like bucket style bags like the Domke F-2 or the Think Tank Retrospective line. They're practical and rugged but Billingham bags have a totally different look and feel to them. Classy but not too fancy. High quality materials only, such as leather and brass.
The Billingham Hadley Large has a very long adjustable shoulder strap wich comes in handy when you're my height. I'm 6'5'' by the way. My bag even came with the optional shoulder pad wich I find awesome. It's very, very grippy and it reduces the amount of preassure applied to the shoulder. I allways wear my bags on my left shoulder, so slippery straps are not really an option.
I really like the quick realease front straps. They're fairly easy to operate with one hand (unlike Domke's metal hooks) and they look really good.
So, what amount of gear can you put in it? Let's see.
The main compartment measures 14⅝" x 3⅜" x 11⅞" and will fit a Canon EOS 5D Mark III with a battery grip, a 70-200mm f/2.8, a 600EX-RT and will still have room for smaller things like memory card holders or foldable flash brackets. If you're a careful person, you can also put a full size iPad between the canvas and the removable insert. I guess you could cram more into the main compartment if you stack things on top of each other, but I very rarely do that.
If you remove the dividers inside the insert you can easily fit a 15" Macbook Pro, thus reducing the room for a camera. I did pack my Fuji X100 and a Macbook once, but I had to remove the lens hood or else it would be too much of a tight fit.
The front pockets measure 7½" x 2¾” x 9⅞” and will if necessary fit another pro size camera each. I use mine for filters, gels, film, notebooks, iPhone, wallet. Yes, they're that big.
In summary, I strongly recommend the Billingham Hadley Large. They look good, they're really dureable and sturdy. Oh, and they're water resistant (I got soaked last weekend but my gear stayed nice and dry). If you like its looks and don't carry around a ton of gear - get one!