Guys, just a FWIW, last fall I bought a LowePro "sling pack" for my SLR system, and this thing is awesome.  It is a bag that slings over the head and one shoulder, then when you want to use it you slide it around in front of your chest and the side unzips for your main camera.  If youwant more stuff, you can take it off and the flap unzips more fully exposing the top, plus other flaps unzip as well...really slick, and beats those camera bags of old as well as inconvenient back packs!