There are lots of other packs out there, some of them lighter than what you're looking at. They may be more comfortable, too--you'll have to try them on. Many of these are framed packs weighing about two pounds (or slightly less). Try doing some searching on this site (see the sticky post at the beginning of the General Discussion section for how to search this site). Here are a few reputable firms to look at online that make lightweight packs with a frame (in many cases removable for lighter loads): ULA-Equipment, Elemental Horizons, Gossamer Gear, Six Moon Designs, Hyperlite Mountain Gear.

As already mentioned, the most important aspects of a pack are fit, fit and fit! The pack must fit your body, it must fit your gear, and it must be comfortable for you to carry with your gear inside. Have all the rest of your gear ready, box it up, and take it to the store. If you order a pack online, have your gear ready to load up the pack and try it out (keeping it clean so it's returnable) as soon as it arrives.

Pack fit is almost as individual as shoe fit, so you need to do lots of trying on!