I appreciate you and others posting your gear lists. I am more of a short-term backpacker, and I when I first decided to do the AT this year I was thinking more of my gear was light enough to avoid replacement, but now I'm thinking several big-ticket items are going to have to be replaced. My pack isn't too bad, an external frame 26.6 oz Jansport that will hold more than I could ever need, but the two biggies, tent and sleeping bag, are WAY heavier than any gear list I've seen. To make matters worse, for 45 oz sleeping bag is only 30 deg. That added weight probably wouldn't be catastrophic if it was a 20 deg, but leaving in late March, April 1st at the latest, I have to consider the weight of whatever else is keeping me warm. My mammoth tent is a Eureka Backcountry -- 85.6 whopping oz. This has obviously got to go, and will be one of the more expensive replacements. I do have a netting system and ultralight tarp that could weigh in at under under two pounds, but I'm not sure I like this for the early colder months.
As far as being used to cold weather... I have been in upstate ny the past few years and -10 days and colder nights are routine some years, but that doesn't make me any more willing to freeze on a long-distance hike. I am never cold when I'm hiking, but once I stop and especially for sleep, I like to be warm. The trail offers enough challenges, I would be willing to carry an extra couple pounds if it keeps me warm enough to sleep at night.
My gear list in case anybody's interested... At this point this is mostly me weighing in existing equipment so I can see where I need to make replacements. Haven't gotten to clothing yet, but I've pulled out all my polyester and don't expect to make many expensive purchases there.
http://lighterpack.com/r/19ercp