To respond to a few of the other comments:
There are fewer services open. But this forces you to stay out in the woods, which I think speeded up our adjustment to our great new life. You end up going into town a lot less in Georgia/N.C./Tennesee… which I would think makes it more like the southbounder experience – they are immediately hit w/ the 100-mile Wilderness. Also, we did not have any trouble resupplying. It just had to be carefully planned. We resupplied at Neels Gap, then Helen, Georgia, and then Franklin, N.C., if I am recalling correctly.
Clothing: What I carried in winter is exactly what I carried and needed in the Whites in July. If you pick your clothes carefully you’ll have enough layers for warmth without too much weight. Yes, your pack is heavier than a summer pack, but I still don’t think that 10-mile days felt like 20-milers (although maybe I should reread my journal. I miss the trail so much that I do not really remember anything “bad” about it! 
I’d agree that the sleeping bag is VERY important. We had 0 degree down bags and got in them as soon as we hit camp. I was never cold at night.
Lastly, I do not know when you are leaving or whether you are going north or south. But leaving when we did, Jan. 31, and headed north definitely did not require serious mountaineering experience. I can tell you that we don’t have it! And the only time I think our experience was truly “unsafe” was not having crampons leaving from Springer. We were very lucky in the Smokies and had great weather, but that’s another place on an early hike that you might need crampons/snowshoes, or something.
The other great thing about an early start is that you do not have to worry about making it to Whites or Katahdin before the bad weather hits.
Linus
Linus