David, I agree with the need for a belt; I have frameless and beltelss packs, but as a LW, not SUL backpacker, carrying 10lbs TBW day hike, 20 lbs TBW camping, I like a frame to transfer the weight off my shoulders to my hips, where a padded belt, not a nylon strap, distributes it circumfrentially. My dayhike framed/belted pack is a Lafuma Race28 at 1100 grams. And my overnight/camping pack is a framed/belted Granite Gear.
I think of this as a tradeoff between hiking comfort and camping comfort. If you are usually moving, light weight is most comfortable. If you are usually stationary, such as base camping, then comfort in the campsite requires more and heavier items. If someone were OCD and anally retentive enough to graph this, it might look like this.
The 'sweet spot' for me depends on the ratio of hiking to camping for a particular trip, using the lightest available gear to meet each performance requirement.
Similar graphs could be made for safety vs. weight, distance vs. weight, etc..