Hi I'm about to go on a year-long backpack/hitchhike/couch-surf trip in New Zealand, and am willing to drop some cash on a big new pack for it. What are everyone's favorite features of their backpacks, or the features they long for, or the features you think are about as useless as cephalopods on rollerskates?

For instance, I am torn between a pack a friend had which was effectively a giant dry-bag with shoulder straps, and lots and lots of easy-access pockets. Also torn between two small packs I can check, that don't have outside pockets, and one giant holds-everything-for-a-month backpack.

If you think you have a perfect pack, or near perfect, what is the make/model? I'd like to check it out.
(I'm 5'6, med-athletic build, female, and have lots and lots of stuff)