A few years ago I got a bag second hand which has turned out to be the most magnificent thing ever. It's getting some wear, now, and some stitching is tearing out, and I'm not sure how much longer I can trust it to carry my stuff. It's a Galen Rowell bag from Photoflex, who of course was not in the bag business for very long.

Things I like about it:
The top opens away from me, so I can get into the bag without the lid being in my way.
The shoulder strap passes through a sliding pad. The pad stays on my shoulder and as I move the bag around the strap slides freely.
The strap fastens to the bag with metal clips on swivels, so it's strong and doesn't twist up.
All the pockets have top zippers, no flaps falling open and dumping stuff out. Not only that, but they're big enough to be useful. I carry a 7x35 binocular in one of the end pockets!
The interior is light-tan in color, so lens caps and the like don't disappear in the darkness.

That all means the most bestest convenience in the world: I can access anything in the bag without setting it down and unpacking. I want to change lenses or mount the flash, I just bring the bag around front, dig through it and get what I need, put the other stuff away, slide the bag around my back out of the way, and continue shooting. No putting stuff down and unpacking, which in the muddy woods is fairly important.

I've got one body, four lenses, a flash, spare battery, charger, AAs for the flash, polarizer filter and adapter rings rings, binoculars, lens cloth, spare lens caps, and even a light meter with which I can measure incident light if I want to. And all of it is reachable with the bag still on my shoulder.

No bag I've tried lets me do that. The cover opens the wrong way, so I have to hold it against my chest while rooting through the bag. The strap has to scrape my neck to move the bag around. The exterior pockets are actually flaps that fall out, along with whatever is in the pockets when you open them.

Every bag I've looked at or tried has to be set down to really get in to it. USELESS!!!!!!

I recently bought a Tamrac 5606 System 6 bag, pretty much because it was about the same size, and I despise it! It carries my camera and lenses, but the outside pockets are flaps or just too small, cover goes the wrong way and has too many fasteners, strap is yucky, blah blah blah.

So, Suggestions? I will NOT consider a backpack!!!! Not in a million years will I consider a backpack. I do NOT want to unpack to get into the bag.