Pack comfort has a tremendous amount to do with what you put into it. If you're carrying a heavier load, then a heavier pack will be nice, although I agree that the Osprey and ULA packs mentioned above might be able to do a similar job with less weight.
But consider a truly ultralight load (say 10-20 pounds). Put these into a really lightweight pack from Gossamer Gear, Ula, Golite, Mountain Laurel Designs, Six Moon Designs, etc. and the comfort will be wonderful. From my experience, there is nothing more comfortable than a 10 pound load in a 4 ounce pack. I punch the pack to conform it to my back and it disappears on my back.
But to each his own! If you love your pack, consider losing weight elsewhere. Or if you're really happy (when it comes to gear, I never am- it's a curse), then just get out and hike. Lots of ways to enjoy the outdoors!