That said, I'm with youI'm working hard these days to pare weight. Part of that effort has been to acquire an Osprey Aether 60 ($199), which carries 3,700 cubic inches in the medium size and weighs three pounds, six ounces. My conclusion: It's fabulous. Carries well, holds more than the size would indicate, and is very cleanly designed. The suspension in particular is first-rate. I wasn't entirely dazzled by the construction, and had to have a mesh bottle pocket repaired straightaway when it blew out. Also had Rainy Pass Repair replace the fixed pad loops with plastic buckle-style loops (for ease of attaching and detaching stuff). Otherwise, I love it. Carries 30 to 35 pounds effortlessly, and is ideal for three- to four-night trips.
Mountainsmith's Auspex ($250; www.mountainsmith.com) carries a bit more and weighs about the same. I haven't used it myself, but I know it's highly regarded. So nothing wrong with that choice, either. The best solution is to find a store that carries both, try them on, and see what you think.