I had used the Tamrac Adventure 7 backpack for about 2-1/2 years, and found it to be adequate for my old equipment. This consisted of an Olympus E510 with standard kit lens, a telephoto lens, a wide angle lens, and a Sony camcorder. I upgraded to a Nikon D600 with 28-300mm lens at Christmas, and used the Tamrac bag for a trip to Hawaii in January 2013. As the D600 does video and the zoom range of the new lens covers the range of two of the Olympus lenses, I figured I would actually save a little weight, and this proved to be the case. Without any additional lenses and no camcorder, the weight was okay and the D600 just about fit. During the trip, however, I noticed that when I set the bag down on a hard surface, I could hear the sound of the lens cap hit the floor. The bottom of the Tamrac bag is padded, but the old Olympus with lens attached did not reach to the bottom of the bag. The longer lens barrel on the 28-300 caused the camera to actually rest on the lens cap, rather than be suspended by the bag from the sides of the camera. I was careful for the remainder of the trip, but I knew I'd have to explore other options soon.Several customers left detailed reviews of the Lowepro Fastpack 250, and the dimensions seemed right, so I went down to a local Best Buy to inspect it in person. The two things that I wanted were: easy access to the camera without it being in a vulnerable position; and non-camera storage space at least equal to that of the Tamrac. I was pleased to find that the Lowepro met both conditions: it has more than the 8 inches of clearance needed for the camera and lens, and the upper storage area is actually slightly larger than that of the Tamrac.Some observations on the new Lowepro:* The main camera section has a dual zipper design that can be completely zipped back to expose all the internal compartments or just enough to open the side to remove the camera with zoom lens attached.* Unlike the Tamrac Adventure 7 which is a clamshell design, the Lowepro can be swung to the side by slipping your right arm out and keeping the bag on your left shoulder. In this position you can open the side of the bag and remove the camera, but none of the additional items stored in the main compartment are in danger of falling out. This might not work as well for left-handers.* To access all of the items, you would have to take the pack completely off and set in on a level surface before completely pulling back the zippers.* The laptop pocket can hold a 15-inch unit with no problem, but would make the pack a lot heavier. Better to carry a 10-inch or smaller tablet there, but the dimensions of the pocket make it ideal for documents, such as a travel folder or full-size magazine. This is a huge advantage over the Tamrac Adventure 7, which did not have a pocket like this.* There is a front pocket that holds all my memory cards, remote control shutter release, extra battery, filters, and mini-tripod with ease. Additional space for memory cards is on the inside of the main compartment zipper cover.* The top storage area has dual zippers, an inside mesh area to hold pens, sunglasses, and other items. I currently have a baseball hat, small umbrella, small binoculars, mobile phone charging cables, and earbuds in there. It's not unusual to also store a paperback book or travel guide, my wife's Canon G15, and a bag of energy bars or cookies.* It has one elastic mesh pocket for a water bottle (the Tamrac Adventrue 7 had two, one on each side).I haven't flown with this bag yet, so I can't tell you how well it fits under the seat in front of me. The Tamrac had no problem, and these are about the same size so it should work fine. The only difference is that the Lowepro is a little more structured so it might not compress as well. We have a Las Vegas trip coming up in May 2013 so I will update this part of the review then.UPDATE OCTOBER 2014 - I've flown with this bag multiple times and can verify that it does fit under most seats with ease. Curiously, the tightest fit was on a newer, larger aircraft, the Boeing 767. When we switched to a Boeing 737 for the connecting flight, the bag fit underneath with plenty of room.Photos:1. Tamrac Adventure 7 and Lowepro Fastpack 250 from front.2. Tamrac Adventure 7 and Lowepro Fastpack 250 from side3. View into top storage area of each4. View into front pouch of each5. Nikon D600 with 28-300mm lens and hood attached fits easily into main camera compartment. Lowepro bag is lying on its back. The Tamrac bag is standing up open in clamshell position and the only way to hold the camera is to put it in lens down, not ideal for a long lens like this.