Owner contribution
love the Tamrac 5275. It's very ergonomically and as you can see fits a LOT of gear although it's mid-sized. Recommend it in every aspect, especially with the Tamrac external lens pockets that fit on your backpack or belt.

For traveling with and protecting a full complement of camera gear, the Expedition 5 Photo Backpack is fully padded with thick, closed-cell foam. Inside, the adjustable foam-padded divider system has foam pillars to cradle and secure a camera with a long lens attached. The bottom is foam-padded with a plastic insert for shock protection. Two Windowpane-Mesh™ pockets keep accessories organized. The foam-padded shoulder straps feature Tamrac's Strap Accessory System™ (S.A.S.™) slots to attach our optional S.A.S.™ components and are held in place with a quick-release sternum strap. Outside, a large front accessory pocket, Modular Accessory System™ (M.A.S.™) attachment slots, a vinyl-reinforced mesh pocket, bungee cord tie down, lash tabs, and Tamrac's QuickClip™ tripod attachment system complete this lightweight, full-featured photo backpack.
love the Tamrac 5275. It's very ergonomically and as you can see fits a LOT of gear although it's mid-sized. Recommend it in every aspect, especially with the Tamrac external lens pockets that fit on your backpack or belt.
After comparing it in the store to the equally sized Lowepro MiniTrekker, I liked the Tamrac features better. It has thicker padding in shoulder straps, more rigid vertical dividers inside, metal D loops for attaching a shoulder strap (and they are mounted, along with the handle, on a supporting strap that goes completely around the bag), 4 side straps for clipping on extra pouches for holding various additional items (Tamrac makes a variety of these modular bags), lighter weight, military grade hardware, bungee cord webbing for strapping on a light rain coat, top inside pocket fits larger items, plus cheaper price. It holds a lot for a medium size backpack, and contrary to what B&H Photo lists in their specs, it does have a nice wide waist belt with quick release buckle, and tripod straps. Theres room to add another lens such as Canon EF 100mm F/2.8 USM Macro Lens (at that point will probably add the external filter case or/and medium case for flash - the Tamrac external modular accessory system (MAS) is a handy option for both expansion and not having to dig around inside the bag for smaller items) My advice to anyone looking for a new bag - after reviewing websites for features, prices, etc of various bags, the most important thing I think is to visit a well stocked local camera store to actually see the various bags for real. This is the only way to really get a good impression of how well it will fit your equipment and to compare and judge the relative sizes and features of various bags. Also, know the length of your lenses and bring a tape measure or your equipment with you to check how well it fits. Some of the large backpacks are like suitcases and are extremely bulky and heavy and that's hard to judge from looking at a website. I actually ended up with a better price at the local shop than online, for both the item and for the tax vs shipping costs. After about a year and a half using the bag, I'm still happy with it. I've added to it though - to make room for two more lenses (a 100mm f/2.8 macro lens & Canon EF 24-70mm f/2.8L USM), I moved the flash unit, filters, etc, into a pair of Tamrac modular accessory pouches attached to the sides... thanks to Brian ZImmerman for comments & photos.