Dave, if you note, in all of the responses, precisely one person, you, mentioned nature.
So let me give you my list of priorities, which goes along somewhat with what you are saying:
1. This one is far above all other factors: to be in nature.
No pack weight I have ever carried has made me unable to achieve 1. And because 1 rules all others, I never actually cared that much about weight. Amusingly, while carrying that weight, I have never seen a UL backpacker in any difficult terrain or climate or weather, particularly not in rainy winters, where usually I see either nobody, or one person. I had hopes for the columbia gorge this July, but was denied, and again I was the only person I saw for 2 days, and the only other backpackers I came across in that time were regular folks, except on the weekend a few miles from the trialhead, then I saw a few guys with lighter packs, with their ipods, of course, to avoid actually hearing anything around them I guess. And that was in the middle of summer 30 miles start from Portland.
Some of the best trips I ever have taken in terms of experiences were with starting weights of over 50 pounds. I had an old friend who did a lot of High Sierra backpacking, he had a thing about dried or freeze dried foods, he hated them, so he carried nuts and trailmix for food, no stove, single wall tent, etc, way ahead of bpl people in that regard, resulting in a pack weight of 80 pounds to start. Given his body weight was probably 140 or so, that's saying a lot. He used pretty light expensive gear too though. One of the best backpackers, and most serious, I've ever known. I never heard him mention a word of complaint about pack weight, nothing. Because it didn't matter, he was achieving his goal, totally, and in exactly the way he wanted. And he'd still be one of the very few people I'd consider going non solo with. I'm not what I'd consider a very tough guy, so I really have to scratch my head at guys who wouldn't go if they had to carry 40 pounds, am/was I really in that great shape? Maybe I am, but it doesn't feel like it.
2. Having a lighter pack really helps here, to 'climb the mountains, and get their good tidings' (quote from John Muir). Or descend to the creeks and valleys, and get their good tidings, the trick is to get them. He's not speaking metaphorically there, I would have thought maybe he was before this year, and hearing those tidings finally, he actually means it. I call it the song of nature. Weight of pack can help you get there, but by no means should it matter that much, after all, if you are too rushed or busy to get the tidings, pack weight isn't going to matter much.
I enjoy the hobby of trimming off weight, a few grams here and there, adding some on, what, you say, I can get a hard steel 0.7 oz 3" blade folding knife? I'm in. 1 million gallon alleged sawyer squeeze at about 3 oz, fantastic, count me in.
And like others here, I've arrived at a weight around 12 pounds give or take one or two, that seems to the actual sort of natural cutoff point. 12 pounds gives me a 25 pound pack for a 7 day trip's start, which is great. If I make my own tarptent I might be able to cutoff one more pound, but I'm not seeing a whole lot of areas to cut, I mean, I still expect to be the only light backpacker I run across in weird terrain or weather, but I will truly enjoy the day I run into one, will be something of a relief to be honest. Maybe we are sort of like mountain lions, where only one is around in each area? Who knows.
After 2. it largely does not matter, I like testing the various ideas I come across here, the materials, myog in particular, very liberating in many ways. I am in camp roughly the same or more time as I am hiking, the trick is to optimize the whole thing, not to sacrifice one for the other, as far as I can see, and that seems totally doable.
Well, ok, food/energy mix, that's fun too, best taste for least weight, that's an interesting one, but that doesn't require anything modern, all you have to do is see how it was done, more or less, then do it. But good super light food, home dried ideally, organic ideally, not junk, count me in there too, that means more miles with more energy and more enjoyment eating that energy.
Best UL type method: alcohol stove, silent, and really helps in 1 and 2, majorly. Total silence, nature is there and listening, and it's cool to not interject some machine roar into the process. Well, and a sawyer squeeze, simpler better and lighter, no moving parts, no chemicals, easy to clean.
personally, I do not count any trip under 3 days as backpacking trip proper, so nothing in terms of gear or weight that is only designed for such a short term scenario interests me that much, ideally 3 nights, 5 nights is really my minimum now, unless I just want to go somewhere to test some gear or ideas.
As a very welcome respite from the excess of some of the ideas of some people here, I picked up a nice pacific crest trail book by national geographic, two guys hiked it all at a point only a few had, in 1974 or so, took two summers. Most of what they are talking about is nature, people, people in nature, and so on. Very little talk of gear, gear just was what you needed to have to do it. Healthy perspective.