"You might like looking at Wired's blog she did the PCT in 2011 and is going to be doing the CDT this year,she gives her gear list and a review for it and her new list for the CDT.She said that she was jealous of the people with ULA packs and got a ULA Curcuit for the CDT."
Ditto. I used a GG Mariposa Plus on the PCT, and overall it worked fine, but I overloaded it going into the Sierras, and carrying a bear can in it was a bit of a PITA. I started with the can strapped to the top but could never really make that work and so shifted to hang a whole lot of stuff on the outside to accomodate the can inside.
The threads holding shoulder straps to the pack started to look alarming in there, so after the Sierras I swapped by mail for my Wife's similar Mariposa plus and finished the trail with that.
I took one of those to start the AT, and got maybe halfway through, and so speculate that that pack did the equivalent of one thru-hike, and it was in somewhat sad shape by then (the waist belt was particularly wonky). I ordered a ULA Circuit by mail and did the second half of the AT in that, and then the CDT in 2011 with it, and a good few hundred miles in it last year, and I plan to do a good few hundred miles in it this year.
The Circuit isn't as light as the GG packs, but it's more durable while still being reasonably light, and it has IMO just the "right" amount of features. I.e., I find it a good balance between weight, cost, durability, capacity, features, and whatever other criteria you can throw in there.