I bought the Lowepro Slingshot 200, couldn't be happier.
It's holding my DSLR + grip, 24-105L, 70-200L, 85mm, 28mm (contax, not bought yet but plenty room for it), Kata Rain cover, hurricane blower, mosquito net, gloves, maglite, 2 filters, 9 CF cards, 2 extra batteries, Whibal, cable release and hotshoe spirit level.
There's still room for a bit more, if I leave out the rain cover or gloves (or the 2 primes) then I can fit a flash or backup body. There are very good and strong attachment points (4 in total) for S&F acessories such as pouches or lens pouches though I don't need them at present. You could even use on of the points for a monopod.
Did I mention that its very small, not at all bulky like the backpacks are and far lighter when empty, fits very comfortably and has a second strap to keep the single strap from bouncing, and is as well made as any lowepro pack. It comes with the usual Lowepro rain cover.
The quick opening system for street shooting is very cool, it also means that even with tripod shooting you don't need to open your entire bag, or take it off your back even to set up, assuming you have the right lens attached. This saves time, and more importantly saves you finding somewhere stable to put your bag and shield it from the elements as you open it.
I'm extremely happy with it.