Lowepro Mini Trekker Classic user here.
It comfortably carries my 20D with 24-70 f2.8, 10-22mm wide angle, 70-200 f2.8, my Canon A85, spare batteries for both cameras, a Jessops 2x TC, remote shutter release and lens hoods for each of my f2.8 lenses. I also used to lug around a Canon 75-300 IS USM lens. and i don't even use all the pockets in it.
I know it's only 3 lenses but every one of them is a 77mm filter so they're all BIG..
I normally carry it over one shoulder but for longer walks i put it on properly and it it's really comfortable. It's amazing how heavy you can make it and still carry it in comfort without straining your back.
It's a great bag and if i ever replace it, it'll be another Lowepro.