By Jing Wen; original article here.
Oh, and for that last reason, these are probably not good bags to buy if you like buying lots of bags on an ongoing basis. One of their main advantages is longevity, and long use is the only thing that will make the high initial outlay sensible. So if you like to buy bags like clothing, constantly switching and swapping and changing styles, a Billingham probably isn't the thing. It's really only for you if you're the type to keep something a long time.
And he adds an interesting observation (and tip) about Billingham bags:
by the way: unless you're a pro—if you're a hobbyist photographer photographing for fun or art or interest: I'd recommend as a guiding principle that you should never carry, and probably not even own, more gear than you can fit into a Billingham Hadley Pro or a Think Tank Retrospective 7. If you have more gear than that, change your gear, not your bag.
Which is, of course, something I believe in. Having too much gear for someone shooting for art leads to distraction of vision, and for someone just shooting for fun, only leads to under-usage. Applies to both carrying and owning gear, to differing degrees.
And that's pretty much why my Billingham Hadley Pro will be my last camera bag - simply because it lasts so long and all the gear I take on my walks fit inside it.