In reply to Cammy:
After working my way through most of the alternatives I ended up with an F-stop Satori. After waiting six weeks or so for delivery I sent an enquiry and it was dispatched the next day. So I get the impression they'll leave you waiting until you ask.
Good news is it fits pretty all your criteria. Big, comfy to carry and very quick access which are my main concerns. It isn't massive though, if you wanted to carry camping kit you'd need to drop at least a lens and a flash or two. With an XL ICU and my large format kit there isn't much room left for more than a waterproof and lunch. The other ICU I've got - large slope - leaves a bit more room but is about the same capacity as a Lowe Mini Trekker - i.e. your kit would be a squeeze.
The outside sheds rain well, but I don't think any rucksacs are properly waterproof so I tend to pack important stuff in exped drybags. You could zip the ICU up too, but I wouldn't expect to walk all day in west coast rain and it stay dry.
Dual ice axe loops plus side compression straps which are adequate for a Gitzo 3-series.
Downsides - very expensive, uncertain delivery time. I bought an end-of-line model which brought the cost down significantly to pricey rather than ludicrous.
Generally over-designed - unlike alpine sacs which have generally gone minimalist this thing is covered in straps, zips and internal storage pockets. I guess this is what appeals to the bells-and-whistles photography crowd but I'm tempted to take a hot knife to it.