Looking at the 3400. My go to pack right now is a Zpacks Zero Medium, which is 2200 ci. I live in western North Carolina, and typically go out for two to three nights, and the occasional week or so when I can get the time off. Usually do between 15 and 20 miles a day. I am going to thru-hike the AT next year, and this is one of the packs I've considered using.
If you have one, what do you like/dislike about? Any other recommendations?

