As technology gets better and better, things begin to get lighter. Now this can be taken advantage of in one of two ways: you can either a) make for a lighter more agile pack, or b) make for a more luxurious camp at night. Usually, the best thing to do is go for a good mix of the two. For the 'ultra light' people, if they get wet, they don't have any extra clothes to change into, they also don't have the comforts that most of us like, especially for longer trips like the AT. If there is something that is an extra 8 ounces, get it; if there is a choice between two items and one is an ounce lighter than the other, but the other you like better, get that one. As long as you're smart about it, and don't go crazy on either side of the spectrum, then you'll be fine -- your back will get used to the pack regardless of weight (for the most part.)
A good pack weight with food and water is between 30-40 lbs, So stay close to that on both sides. If you start to dip under 30, you're either missing something, or you're not going to be prepared for everything, and over 40, you're just carrying too much.
So each post will be another item in my pack, how I felt about it, and how well/long it lasted -- I hope this helps.